Syndemic
Encyclopedia
Syndemic refers to the aggregation of two or more diseases in a population in which there is some level of positive biological interaction that exacerbates the negative health effects of any or all of the diseases. The term syndemic was developed and introduced by Merrill Singer
in several articles in the mid-1990s and has since received growing attention and use among epidemiologists
and medical anthropologists
concerned with community health and the effects of social conditions on health, culminating in a recent textbook. Syndemics tend to develop under conditions of health disparity, caused by poverty
, stress, or structural violence
, and contribute to a significant burden of disease
in affected populations. The term syndemic is further reserved to label the consequential interactions between concurrent or sequential diseases in a population and in relation to the social conditions that cluster the diseases within the population.
The traditional biomedical approach to disease is characterized by an effort to diagnostically isolate, study, and treat diseases as if they were distinct entities that existed in nature separate from other diseases and independent of the social contexts in which they are found. This singular approach proved useful historically in focusing medical attention on the immediate causes and biological expressions of disease and contributed, as a result, to the emergence of targeted modern biomedical treatments for specific diseases, many of which have been successful. As knowledge about diseases has advanced, it is increasingly realized that diseases are not independent and that synergistic disease interactions are of considerable importance for prognosis
. Given that social conditions can contribute to the clustering, form and progression of disease at the individual and population level, there is growing interest in the health sciences on syndemics.
, coinfection
and associated terms. The differences between “comorbid” and “syndemic” are not merely semantic. As Mustanski et al. (2008:40) explain: “comorbidity research tends to focus on the nosological issues of boundaries and overlap of diagnoses, while syndemic research focuses on communities experiencing co-occurring epidemics that additively increase negative health consequences.” Consequently, it is possible for two afflictions to be comorbid, but not be syndemic (i.e., the disorders are not epidemic
in the studied population or their co-occurrence is not accompanied by worsened health). Thus, two (or more) diseases can be comorbid but no interaction occurs between them, while in other cases interaction occurs but it has beneficial rather than deleterious consequences. Syndemic theory seeks to draw attention to and provide a framework for the analysis of adverse disease interactions, including their causes and consequences for human life and well-being.
, Mycobacterium avium), fungal (e.g. candidiasis
), protozoal (e.g. toxoplasmosis
), and viral (e.g. Human Papilloma Virus) infections and possibly viral-caused malignancies (Kaposi's Sarcoma
). Similarly, there is evidence that periodontitis, which can lead to tooth loss
, may arise from a syndemic. Periodontitis is known to be caused by bacteria of several different species (e.g., Porphyromonas gingivalis
, Dialister pneumosintes, Prevotella intermedia
) that adhere to and reproduce on tooth surfaces, especially under the gum line. Multiplication of these pathogens may be inhibited by bodily defenses unless these are weakened by a herpesvirus infection of the periodontium
.
Another type of syndemic relationship involves one disease enhancing the virulence of another. There is evidence, for example, that herpesvirus has this effect on HIV infection, with progression to AIDS being significantly accelerated by co-infection with herpesvirus. Similarly, in gum infection, periodontal bacteria may enhance the virulence of herpesvirus.
Alternately, one disease can assist the physical transmission of another disease. This appears to be the case, for example, with syphilis and HIV coinfection as a result of genital-tract ulceration caused by the former supporting sexual transmission of the latter.
Direct interaction of diseases is in the case of genetic recombination
among different pathogens, for instance between Avian sarcoma leukosis virus
and Marek's disease
virus (MDV) in domestic fowl. Both of these cancer-causing viruses are known to infect the same poultry flock, the same chicken, and, even the same anatomic cell. In coinfected cells, the retroviral DNA of the avian leukosis virus can integrate into the MDV genome, producing altered biological properties compared to those of the parental MDV. The frequency of gene reassortment among human pathogens is less clear than is the case among plant or some animal species but of significant potential concern as animal diseases adapt to human hosts—which they have been doing at an increasingly rapid pace—and as new diseases come into contact.
In some cases, coinfection
may open up multiple syndemic pathways. In studies of human populations, a lethal synergism has been identified between influenza virus and pneumococcus, a likely cause of excess mortality from secondary bacterial pneumonia during influenza epidemics. There is a significant level of evidence indicating that the influenza virus alters the lungs in ways that increase the adherence, invasion and induction of disease by pneumococcus. But other consequential changes, such as alteration of the immune response which weakens the body’s ability to clear pneumococcus (or, alternately, by amplifying the inflammatory cascade), are also suggested by existing research.
In other cases, syndemic interaction among diseases is apparent but the pathways of linkage are not yet clear. An example is the apparent interaction that occurs between type 2 diabetes mellitus and hepatitis C viral infection. Several factors are known to contribute to the onset of type 2 diabetes, including diet, obesity and aging. The role of infection, however, is only beginning to be understood. Already it is known that risk for serious infections of various kinds increase significantly with poor diabetes control, but appreciation of more complex relationships between infection and type 2 diabetes is now emerging as well.
infection. This finding was the product of a study of HIV-infected children living in Zambia. In the study, children who had measles, and reported various typical symptoms, including fever, rash, conjunctivitis, runny nose, and cough, had a significant drop in HIV levels detectable in the blood as compared to HIV-infected children who were not infected with measles. Several potential mechanisms could be responsible for the temporary suppression of HIV replication early in the course of a measles infection. Morbillivirus (measles virus) infection is known to cause lymphopenia, a reduction in the number of CD4+ T lymphocytes circulating in the blood. The low point in lymphocyte levels occurs just prior to the onset of the distinct red circular skin rash (called rubeola) characteristic of a measles infection. Within a month of this nadir, the number of lymphocytes tends to return to normal levels. The drop in HIV may reflect a decrease in target CD4+ T cells needed for replication. Alternately, measles virus infection may stimulate the production of cells that are directly responsible for suppressing HIV replication. Several candidates have been suggested, including the β-chemokines, CD8+ cell antiviral factor, and the cytokines known as IL-10 and IL-16 (biochemicals that inhibit HIV transcription), but none has been confirmed as the source of HIV suppression. Additionally, Moss and co-workers found that median plasma levels of RANTES, a chemokine that attracts immune system components like eosinophils (a kind of white blood cell that destroys parasitic organisms), monocytes (a precursor of macrophages), and lymphocytes, were higher in HIV-infected children with measles than in those without measles. HIV suppression also has been identified in patients suffering tsutsugamushi disease, a mite-borne infection found in Asia and Australia, also known as scrub typhus, although the how this occurs is not clear. Other counter-syndemics are likely to be discovered as a syndemic perspective emphazing paying attention to processes and relationships diffuses among researchers.
means "brought forth by a healer" (iatro is the Greek word for healer) and almost always is used to refer to adverse health conditions caused by medical treatment (such as unwelcome side effects
). Can there be iatrogenic syndemics? In principle, this is possible if medical treatment or medical research is involved in creating conditions that increase the likelihood that two or more diseases come together in a population. An example of this scenario would be the use of gene splicing to unite two pathogenic agents and introducing the resulting novel organism into a population. There is a possibility that this precise event occurred, for example, during a randomized, double-blind clinical trial testing the efficacy of the prototype HIV vaccine called V520. On November 6, 2007, the pharmaceutical manufacturer Merck & Co. announced that research on the drug had been stopped because interim findings showed that there appeared to be an increased risk for HIV infection among participants in the vaccine arm of the study compared to those in the placebo group. Specifically, results showed that of the 741 volunteers in the vaccine group, 24 developed HIV infection (3.2%), while among the 762 volunteers in the placebo arm of the trial, 21 developed HIV (2.75%). Notably, investigators in the study reported a higher risk of HIV infection was found among participants who had an existing immunity to the common cold virus (known as adenovirus type 5 or Ad5). The vaccine was created using a mixture of three components, each of which was made in the laboratory with a replication-defective version of Ad5. This was the organism selected to serve as a carrier, or delivery vector, for three synthetically produced HIV genes. Researchers suggested one explanation for the higher rate of HIV infection among individuals in the treatment group was that the vaccine lowered defenses against the human immunodeficiency virus. In other words, novel organisms created through splicing of genes from two naturally occurring pathogens may have increased the rate of disease. While other explanations of the results exist, the study suggests the possibility of the emergence of syndemics with an iatrogenic origin.
, malaria
and HIV/AIDS syndemic: the Chagas disease
, rheumatic heart disease and congestive heart failure
syndemic: the possible asthma
and infectious disease
syndemic: the malnutrition
and depression
syndemic: the TB, HIV and violence
syndemic: the whooping cough, influenza
, tuberculosis
syndemic; the HIV and STD
syndemic; the stress
and obesity
syndemic, and the mental health
and HIV/AIDS syndemic. Additional syndemics are being identified around the world as public health officials, researchers, and service providers begin to focus on the connections among diseases and the social context factors that foster disease concentration and interactions. In January 2006, in a speech at the Enhancing the Healing Environment conference hosted by The Prince's Foundation for the Built Environment and The King's Fund, St James's Palace, London, Prince Charles, The Prince of Wales, noted the importance of paying attention to the built environment, physical inactivity and the obesity
/diabetes syndemic.
It is estimated that in 1860 there were well over 10 million bison
living on the American Plains
. By the early 1880s, the last of the great herds of bison upon which Plains Indian peoples like the Sioux
were dependent as a food source were gone, victims of economic greed as well as a conscious plan to control Plains Indian populations. White hunting parties scoured the region, sometimes shooting hundreds or even thousands of bison a day. At the same time, after the U.S. military's defeat at the Battle of the Little Bighorn
in 1876, there was a concerted effort to beat the Sioux into total submission. Thus, in 1872, Secretary of the Interior Columbus Delano
stated: “as they become convinced that they can no longer rely upon the supply of game for their support, they will return to the more reliable source of subsistence [i.e., farming]." As a result, they were forced to give up their struggle for an independent existence on their own lands and take up reservation life at the mercy of government authority. Treaties that were signed with the Sioux in 1868 and 1876 stipulated that they would be provided with government annuities and provisions in payment for sections of their land and with the expectation among federal representatives that the Sioux would become farmers on individually held plots of land. The Sioux found themselves confined on a series of small reservations where they were treated as a conquered people. Moreover, as was typical of treaties with Native peoples, the government reneged on its promises. The food that was provided to the Sioux was insufficient and of low quality. Black Elk
, a noted Sioux folk healer, told his biographer: “There was hunger among my people before I went across the big water [to Europe in 1886], because the Wasichus [whites] did not give us all the food they promised in the Black Hills treaty... But it was worse when I came back [1889]. My people looked pitiful… We could not eat lies and there was nothing we could do.” Under extremely stressful conditions, and with inadequate diets, as well as being the victims of overt racism on the part of the registration agents appointed to oversee Indian reserves, the Sioux confronted exposure to infectious disease transmitted from contact with whites. While knowledge about the epidemiology of the Sioux from this period is limited, James Mooney
, an anthropologist and representative of the Bureau of Indian Affairs
sent to investigate a possible Sioux rebellion, described the health situation on the reservation in 1896: “In 1888 their cattle had been diminished by disease. In 1889, their crops were a failure ... Thus followed epidemics of measles, grippe [influenza], and whooping cough Pertussis
, in rapid succession and with terrible fatal results…” Similarly, the Handbook of American Indians notes, “The least hopeful conditions in this respect prevail among the Dakota [Sioux] and other tribes of the colder northern regions, where pulmonary tuberculosis and scrofula are very common… Other more common diseases, are various forms of, bronchitis… pneumonia, pleurisy
, and measles
in the young. Whooping cough is also met with.” Indian children who were removed to white boarding schools were diagnosed with a wide range of diseases, including tuberculosis, trachoma, measles, small pox, whooping cough, influenza, and pneumonia.
As these accounts suggest, it is likely that the Sioux were victims of a syndemic that combined a number of interacting infectious diseases, inadequate diet, and stressful and extremely disheartening life conditions, including, with events like the massacre at Wounded Knee
in 1890 and the murder of their leader Sitting Bull
, outright brutalization. As a result, while the official mortality rate on the reservation was between one and two percent, the death rate was probably closer to 10 percent, a devastatingly high figure.
pandemics during the 20th century that caused widespread illness, mortality, social disruption, and significant economic losses. These occurred in 1918, 1957, and 1968. In each case, mortality rates were determined primarily by five factors: the number of people who became infected, the virulence of the virus causing the pandemic, the speed of global spread, the underlying features and vulnerabilities of the most affected populations, and the effectiveness and timeliness of the prevention and treatment measures that were implemented. These factors unite a range of bio-social causal forces, including production, communication, and transportation technologies; the medical and public health infrastructures; the specific pathogens involved and the nature of their interactions with human hosts; and the pre-existing health status of patients. All of these, in turn, are shaped, to greater or somewhat lesser degree, by overarching political economic structures globally and locally. Epidemics, in short, including their emergence, course, and impact (and whether they become widespread pandemics that exact a sorrowful toll on life and well-being) are sculpted by the configuration of human social relationships including prevailing patterns of social inequality.
The 1957 pandemic was caused by the Asian influenza virus (known as the H2N2 strain), a novel influenza variety to which humans had not yet developed immunities. The death toll of the 1957 pandemic is estimated to have been around two million globally, with approximately 70,000 deaths in the United States. A little over a decade later, the comparatively mild Hong Kong influenza pandemic erupted due to the spread of a virus strain (H3N2) that genetically was related to the more deadly form seen in 1957. The pandemic was responsible for about one million deaths around the world, almost 34,000 of which were in the United States. In both of these pandemics, death may not have been due only to the primary viral infection, but also to secondary bacterial infections among influenza patients; in short, they were caused by a viral/bacterial syndemic (but see Chatterjee 2007).
The worst of the 20 century influenza pandemics was the 1918 outbreak, which epidemiologists estimate was responsible for the deaths of between 40-100 million people worldwide, making it one of the most deadly events in human history. More people died of the so-called Spanish flu
(caused by the H1N1 viral strain) pandemic in the single year of 1918 than during all four-years of the Black Death
(Bubonic plague
) scourge that lasted from 1347 to 1351 (although a significantly higher percentage of the world’s population died of the plague than of Spanish flu). It is estimated that between 20-40 percent of the world’s population became ill during the 1918 pandemic.
The pandemic had devastating effects as disease spread along trade and shipping routes and other corridors of human movement until it had circled the globe. In places like India, the mortality rate reached 50 per 1,000 population. Arriving during the closing phase of the World War I, the pandemic had a significant impact on mobilized national armies. Half of U.S. soldiers who died in the “Great War,” for example, were victims of influenza not of enemy bombs and bullets. It is estimated that almost ¾ of a million Americans died during the pandemic. As noted by one alarmed scientific observer at the time, “[if the pandemic continues] civilization could easily disappear from the face of the earth within a matter of a few more weeks”. In part, the death toll during the pandemic was caused by viral pneumonia characterized by extensive bleeding in the lungs resulting in suffocation. Many victims died within 48 hours of the appearance of the first symptom. In fact, it was not uncommon for people who appeared to be quite healthy in the morning to have died by sunset. Among those who survived the first several days, however, many died of secondary bacterial pneumonia. Moreover, it has been argued that countless numbers of those who expired quickly from the disease were co-infected with tuberculosis, which would explain the notable plummet in TB cases after 1918 (because so many carriers of the disease perished during the influenza pandemic). Again, as seen with the previous two 20th century global influenza outbreaks, disease interaction appears to have been critical, underlining the importance of syndemics more generally in the production of major public health crises.
, characterized by episodic inflammation and narrowing of small airway passages in the lungs, affects about 8 percent of the U.S. population, but the rate of affected individuals has been steadily climbing in recent years, especially in low income, ethnic minority neighborhoods in cities. Thus, in 1980 asthma was found to affect only about three percent of the U.S. population according to the U.S. Centers for Disease Control and Prevention. Asthma among children has been increasing at an even faster pace than among adults, with the percentage of children with asthma going up from 3.6 percent in 1980 to 9 percent in 2005. Among ethnic minority populations, Puerto Ricans the rate of asthma is 125 percent higher than non-Hispanic white people and 80 percent higher than non-Hispanic black people. The asthma prevalence among American Indians, Alaska Natives and black people is 25 percent higher than white people. As is so often the case with health, including health conditions directly affected by global warming, the poor and marginalized suffer the gravest consequences.
Increases in rates of asthma have occurred despite improvements in air quality produced by the passage and enforcement of clean air legislation, such as both the Clean Air Act of 1963 and the Clean Air Act of 1990 in the United States. In other words, existing legislation and regulation have not kept pace with changing climatic conditions and their health consequences. Compounding the problem of air quality is the fact that air-borne pollens have been found to attach themselves to diesel particles from truck or other vehicular exhaust floating in the air, resulting in heightened rates of asthma in areas where busy roads bisect densely populated areas, most notably in poorer inner city areas. Research by the American Cancer Society found that a six percent increase in cardiopulmonary deaths occurs for every elevation of 10 μg/m3 in particulate matter concentration in the air. Exhaust from the burning of diesel fuel is a complex mixture of vapors, gases, and fine particles, including over 40 known pollutants like nitrogen oxide and known or suspected carcinogenic substances such as benzene, arsenic, and formaldehyde. Exposure to diesel exhaust irritates the eyes, nose, throat and lungs, causing coughs, headaches, light headedness and nausea, while causing people with allergies to be more susceptible allergy triggers like dust or pollen. Many particles in disease fuel are so tiny they are able to penetrate deep into the lungs when inhaled. Importantly, diesel fuel particles appear to have even greater immunologic effects in the presence of environmental allergens than they do alone. According Robert Pandya and co-workers who are studying the role of diesel fuel in asthma, “This immunologic evidence may help explain the epidemiologic studies indicating that children living along major trucking thoroughfares are at increased risk for asthmatic and allergic symptoms and are more likely to have objective evidence of respiratory dysfunction.”
Importantly, the damaging effects of diesel fuel pollution appears to go significantly beyond playing a synergistic role in the development of asthma. Recent research suggests that exposure to a combination of microscopic diesel fuel particles among people with high blood cholesterol (i.e., low-density lipoprotein, LDL or “bad cholesterol”) increases the risk for both heart attack and stroke significantly above levels found among those exposed to only one of these health risks. According to André Nel, Chief of Nanomedicine at the David Geffen School of Medicine at UCLA who led the study of duel exposure, “When you add one plus one, it normally totals two… But we found that adding diesel particles to cholesterol fats equals three. Their combination creates a dangerous synergy that wreaks cardiovascular havoc far beyond what's caused by the diesel or cholesterol alone.” The synergy begins when free radical molecules that are attached to diesel exhaust particles enter the body through the lungs and pass into the circulatory system. Another source of free radicals is the fatty acids that comprise LDL cholesterol, which produce free radicals during cell metabolism. Free radical molecules are highly unstable because they have an odd number of electrons in their outer ring. As a result, they react quickly with other compounds in order to “steal” an electron and gain stability. When the "victimized" molecule loses its electron, it, in turn, becomes a free radical and a chain reaction called oxidation is produced that is known to be damaging to living cells and tissues. Of interest to the Los Angeles research team was the consequences of both sources of free radical production coming into contact. Experimentation revealed that the two mechanisms worked in tandem to stimulate genes that promote cell inflammation, a primary risk for hardening and blockage of blood vessels (atherosclerosis
) and, as narrowed arteries collect cholesterol deposits and trigger blood clots, for heart attacks and strokes as well. Atherosclerotic cardiovascular disease is the leading cause of death in developed countries.
is a simplified representation using mathematical language to describe natural, mechanical or social system dynamics. In the early 20th century, epidemiologists became increasingly interested in the use of mathematical modelling procedures to project possible patterns in the spread of infectious diseases, including potential outcomes of an epidemic. To achieve these goals, epidemiological modelers unite several types of information and analytic capacity, including: 1) mathematical equations and computational algorithms; 2) computer technology; 3) epidemiological knowledge about infectious disease dynamics, including information about specific pathogens and disease vectors; and 4) research data on social conditions and human behavior. Mathematical modelling in epidemiology
is now being applied to syndemics. Abu-Raddad, Patnaik, and Kublin (2006), for example, used modelling to quantify the syndemic effects of malaria and HIV in sub-Saharan Africa based on research in Kisumu, Kenya. These researchers point out that infection with HIV facilitates disease progression in individuals exposed to malaria. At the same time, immune reaction to malaria doubles the infectious level of HIV infected individual. In short, in typical syndemic fashion, each of these diseases amplifies the effects of the other. Using mathematical modelling, Abu-Raddad and co-workers found that 5% of HIV infections (or 8,500 cases of HIV since 1980) in Kisumu are the result of the higher HIV infectiousness of malaria-infected HIV patients. Additionally, their model attributed 10% of adult malaria episodes (or almost one million excess malaria infections since 1980) to the greater susceptibility of HIV infected individuals to malaria. Their model also suggests that HIV has contributed to the wider geographic spread of malaria in Africa, a process previously thought to be the consequence primarily of global warming. Other researchers (e.g., Herring and Sattenspiel 2007) also have begun to apply mathematical modelling to syndemics. Modelling offers an enormously useful tool for anticipating future syndemics, including eco-syndemic, based on information about the spread of various diseases across the planet and the consequent co-infections and disease interactions that will result.
In this regard, Jeremy Lauer and colleges (2003) have developed PopMod, a longitudinal population tool that models distinct and possibly interacting diseases. Unlike other life-table population models, PopMod is specifically designed to not assume the statistical independence of the diseases of interest. The PopMod has several intended purposes, including describing the time evolution of population health for standard demographic purposes (such as estimating healthy life expectancy in a population), and providing a standard measure of effectiveness for health interventions and cost-effectiveness analysis. PopMod is used as one of the standard tools of the World Health Organization’s (WHO
) CHOICE (Choosing Interventions that are Cost-Effective) program, an initiative designed to provide national health policy makers in the WHO’s 14 epidemiological sub-regions around the world with findings on a range of health intervention costs and effects.
is contributing to the spread of diseases to new areas and to the potential for new disease interactions. Already it is clear that as a result of global warming infectious diseases such as West Nile Virus
are spreading to new places. Similarly malaria is now found in new places because it is spread by particular mosquito species that are migrating to new locations as a result of changing climates. As a consequence, diseases that did not often interact in the past---through co-infection of the same individuals within a population---may begin interacting more regularly. Finally, there is a need for a better understanding of how the public health systems and communities can best respond to and limit the health consequences of syndemics. Systems are needed to monitor the emergence of syndemics and to allow early-bird medical and public health responses designed to lessen their impact. Systematic ethno-epidemiological surveillance with populations subject to multiple social stressors must be one component of such a monitoring system. Current efforts by researchers at the CDC to expand the discussion of syndemics in public health discourse is an important step in the development of a funded research agenda that addresses these research needs. Given the nature of syndemics, this research requires a bio-cultural/social approach that attends to both clinical and social processes.
Merrill Singer
Merrill Singer is a medical anthropologist with a dual appointment in the Department of Anthropology and the Center for Health, Intervention and Prevention, University of Connecticut. He is also a professor in the Department of Community Medicine and Health Care at the University of Connecticut...
in several articles in the mid-1990s and has since received growing attention and use among epidemiologists
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
and medical anthropologists
Medical anthropology
Medical anthropology is an interdisciplinary field which studies "human health and disease, health care systems, and biocultural adaptation". It views humans from multidimensional and ecological perspectives...
concerned with community health and the effects of social conditions on health, culminating in a recent textbook. Syndemics tend to develop under conditions of health disparity, caused by poverty
Poverty
Poverty is the lack of a certain amount of material possessions or money. Absolute poverty or destitution is inability to afford basic human needs, which commonly includes clean and fresh water, nutrition, health care, education, clothing and shelter. About 1.7 billion people are estimated to live...
, stress, or structural violence
Structural violence
Structural violence is a term first used in the 1960s commonly ascribed to Johan Galtung. It refers to a form of violence where some social structure or social institution harms people by preventing them from meeting their basic needs. Institutionalized elitism, ethnocentrism, classism, racism,...
, and contribute to a significant burden of disease
Disease burden
Disease burden is the impact of a health problem in an area measured by financial cost, mortality, morbidity, or other indicators. It is often quantified in terms of quality-adjusted life years or disability-adjusted life years , which combine the burden due to both death and morbidity into one...
in affected populations. The term syndemic is further reserved to label the consequential interactions between concurrent or sequential diseases in a population and in relation to the social conditions that cluster the diseases within the population.
The traditional biomedical approach to disease is characterized by an effort to diagnostically isolate, study, and treat diseases as if they were distinct entities that existed in nature separate from other diseases and independent of the social contexts in which they are found. This singular approach proved useful historically in focusing medical attention on the immediate causes and biological expressions of disease and contributed, as a result, to the emergence of targeted modern biomedical treatments for specific diseases, many of which have been successful. As knowledge about diseases has advanced, it is increasingly realized that diseases are not independent and that synergistic disease interactions are of considerable importance for prognosis
Prognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
. Given that social conditions can contribute to the clustering, form and progression of disease at the individual and population level, there is growing interest in the health sciences on syndemics.
Cooccurrence versus syndemism
Disease cooccurrence, with or without interactions, is known as comorbidityComorbidity
In medicine, comorbidity is either the presence of one or more disorders in addition to a primary disease or disorder, or the effect of such additional disorders or diseases.- In medicine :...
, coinfection
Coinfection
In parasitology, coinfection is the term used to describe the simultaneous infection of a host by multiple pathogen species. In virology, coinfection can also refer to the simultaneous infection of a single cell by two or more virus particles...
and associated terms. The differences between “comorbid” and “syndemic” are not merely semantic. As Mustanski et al. (2008:40) explain: “comorbidity research tends to focus on the nosological issues of boundaries and overlap of diagnoses, while syndemic research focuses on communities experiencing co-occurring epidemics that additively increase negative health consequences.” Consequently, it is possible for two afflictions to be comorbid, but not be syndemic (i.e., the disorders are not epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...
in the studied population or their co-occurrence is not accompanied by worsened health). Thus, two (or more) diseases can be comorbid but no interaction occurs between them, while in other cases interaction occurs but it has beneficial rather than deleterious consequences. Syndemic theory seeks to draw attention to and provide a framework for the analysis of adverse disease interactions, including their causes and consequences for human life and well-being.
Types of disease interaction
Interest in the syndemics perspective has been driven by growing evidence of the regularity of interactions among diseases and recognition that this interaction influences disease course, expression, severity, transmission, and diffusion. Several different kinds of interaction among diseases have been described, including both indirect (changes caused by one disease that facilitate another through an intermediary) and direct interface (diseases act in direct tandem). In some syndemic interactions—such as the one between diabetes and SARS--changes in biochemistry or damage to organ systems caused by one disease (in this case, diabetes), such as weakening of the immune system, promotes the progression of another disease (SARS). This type of relationship also connects HIV infection and a host of “opportunistic” bacterial (e.g. mycobacterial (Mycobacterium tuberculosisMycobacterium tuberculosis
Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...
, Mycobacterium avium), fungal (e.g. candidiasis
Candidiasis
Thrush redirects here. For the hoof infection see Thrush .Candidiasis or thrush is a fungal infection of any of the Candida species , of which Candida albicans is the most common...
), protozoal (e.g. toxoplasmosis
Toxoplasmosis
Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid family. Animals are infected by eating infected meat, by ingestion of feces of a cat that has itself...
), and viral (e.g. Human Papilloma Virus) infections and possibly viral-caused malignancies (Kaposi's Sarcoma
Kaposi's sarcoma
Kaposi's sarcoma is a tumor caused by Human herpesvirus 8 , also known as Kaposi's sarcoma-associated herpesvirus . It was originally described by Moritz Kaposi , a Hungarian dermatologist practicing at the University of Vienna in 1872. It became more widely known as one of the AIDS defining...
). Similarly, there is evidence that periodontitis, which can lead to tooth loss
Tooth loss
Tooth loss is when one or more teeth come loose and fall out. Tooth loss is normal for deciduous teeth , when they are replaced by a person's adult teeth. Otherwise, losing teeth is undesirable and is the result of injury or disease, such as mouth trauma, tooth injury, tooth decay, and gum disease...
, may arise from a syndemic. Periodontitis is known to be caused by bacteria of several different species (e.g., Porphyromonas gingivalis
Porphyromonas gingivalis
Porphyromonas gingivalis belongs to the phylum Bacteroidetes and is a non-motile, gram-negative, rod-shaped, anaerobic pathogenic bacterium. It forms black colonies on blood agar....
, Dialister pneumosintes, Prevotella intermedia
Prevotella intermedia
Prevotella intermedia is a gram-negative obligate anaerobic pathogen involved in periodontal infections, including gingivitis and periodontitis, and often found in Acute necrotizing ulcerative gingivitis . It is commonly isolated from Dentoalveolar abscesses, where obligate anaerobes...
) that adhere to and reproduce on tooth surfaces, especially under the gum line. Multiplication of these pathogens may be inhibited by bodily defenses unless these are weakened by a herpesvirus infection of the periodontium
Periodontium
Periodontium refers to the specialized tissues that both surround and support the teeth, maintaining them in the maxillary and mandibular bones. The word comes from the Greek terms peri-, meaning "around" and -odons, meaning "tooth." Literally taken, it means that which is "around the tooth"...
.
Another type of syndemic relationship involves one disease enhancing the virulence of another. There is evidence, for example, that herpesvirus has this effect on HIV infection, with progression to AIDS being significantly accelerated by co-infection with herpesvirus. Similarly, in gum infection, periodontal bacteria may enhance the virulence of herpesvirus.
Alternately, one disease can assist the physical transmission of another disease. This appears to be the case, for example, with syphilis and HIV coinfection as a result of genital-tract ulceration caused by the former supporting sexual transmission of the latter.
Direct interaction of diseases is in the case of genetic recombination
Genetic recombination
Genetic recombination is a process by which a molecule of nucleic acid is broken and then joined to a different one. Recombination can occur between similar molecules of DNA, as in homologous recombination, or dissimilar molecules, as in non-homologous end joining. Recombination is a common method...
among different pathogens, for instance between Avian sarcoma leukosis virus
Avian Sarcoma Leukosis Virus
Avian sarcoma leukosis virus is an endogenous retrovirus that infects and can lead to cancer in chickens; experimentally it can infect other species of birds and mammals. ASLV replicates in chicken embryo fibroblasts, the cells that contribute to the formation of connective tissues...
and Marek's disease
Marek's disease
Marek's disease is a highly contagious viral neoplastic disease in chickens. It is named after József Marek, a Hungarian veterinarian. Occasionally misdiagnosed as an abtissue pathology it is caused by an alphaherpesvirus known as 'Marek's disease virus' or Gallid herpesvirus 2...
virus (MDV) in domestic fowl. Both of these cancer-causing viruses are known to infect the same poultry flock, the same chicken, and, even the same anatomic cell. In coinfected cells, the retroviral DNA of the avian leukosis virus can integrate into the MDV genome, producing altered biological properties compared to those of the parental MDV. The frequency of gene reassortment among human pathogens is less clear than is the case among plant or some animal species but of significant potential concern as animal diseases adapt to human hosts—which they have been doing at an increasingly rapid pace—and as new diseases come into contact.
In some cases, coinfection
Coinfection
In parasitology, coinfection is the term used to describe the simultaneous infection of a host by multiple pathogen species. In virology, coinfection can also refer to the simultaneous infection of a single cell by two or more virus particles...
may open up multiple syndemic pathways. In studies of human populations, a lethal synergism has been identified between influenza virus and pneumococcus, a likely cause of excess mortality from secondary bacterial pneumonia during influenza epidemics. There is a significant level of evidence indicating that the influenza virus alters the lungs in ways that increase the adherence, invasion and induction of disease by pneumococcus. But other consequential changes, such as alteration of the immune response which weakens the body’s ability to clear pneumococcus (or, alternately, by amplifying the inflammatory cascade), are also suggested by existing research.
In other cases, syndemic interaction among diseases is apparent but the pathways of linkage are not yet clear. An example is the apparent interaction that occurs between type 2 diabetes mellitus and hepatitis C viral infection. Several factors are known to contribute to the onset of type 2 diabetes, including diet, obesity and aging. The role of infection, however, is only beginning to be understood. Already it is known that risk for serious infections of various kinds increase significantly with poor diabetes control, but appreciation of more complex relationships between infection and type 2 diabetes is now emerging as well.
Counter-syndemics
Discussion of deleterious disease interactions raises a question about the possibility of an opposite kind of disease interaction, namely: are there counter syndemics, disease interactions that lower the burden of disease in a population below the sum effects of the individual diseases involved? The discovery of counter-syndemics is important because such entities may suggest novel strategies for the prevention and treatment of disease. Recent research findings suggest that counter-syndemics do occur and are part of the complex world of co-morbidity. For example, William Moss and fellow researchers at the Johns Hopkins Bloomberg School of Public Health have found that human immunodeficiency virus is transiently suppressed during an acute measlesMeasles
Measles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...
infection. This finding was the product of a study of HIV-infected children living in Zambia. In the study, children who had measles, and reported various typical symptoms, including fever, rash, conjunctivitis, runny nose, and cough, had a significant drop in HIV levels detectable in the blood as compared to HIV-infected children who were not infected with measles. Several potential mechanisms could be responsible for the temporary suppression of HIV replication early in the course of a measles infection. Morbillivirus (measles virus) infection is known to cause lymphopenia, a reduction in the number of CD4+ T lymphocytes circulating in the blood. The low point in lymphocyte levels occurs just prior to the onset of the distinct red circular skin rash (called rubeola) characteristic of a measles infection. Within a month of this nadir, the number of lymphocytes tends to return to normal levels. The drop in HIV may reflect a decrease in target CD4+ T cells needed for replication. Alternately, measles virus infection may stimulate the production of cells that are directly responsible for suppressing HIV replication. Several candidates have been suggested, including the β-chemokines, CD8+ cell antiviral factor, and the cytokines known as IL-10 and IL-16 (biochemicals that inhibit HIV transcription), but none has been confirmed as the source of HIV suppression. Additionally, Moss and co-workers found that median plasma levels of RANTES, a chemokine that attracts immune system components like eosinophils (a kind of white blood cell that destroys parasitic organisms), monocytes (a precursor of macrophages), and lymphocytes, were higher in HIV-infected children with measles than in those without measles. HIV suppression also has been identified in patients suffering tsutsugamushi disease, a mite-borne infection found in Asia and Australia, also known as scrub typhus, although the how this occurs is not clear. Other counter-syndemics are likely to be discovered as a syndemic perspective emphazing paying attention to processes and relationships diffuses among researchers.
Iatrogenic syndemics
The term iatrogenesisIatrogenesis
Iatrogenesis, or an iatrogenic artifact is an inadvertent adverse effect or complication resulting from medical treatment or advice, including that of psychologists, therapists, pharmacists, nurses, physicians and dentists...
means "brought forth by a healer" (iatro is the Greek word for healer) and almost always is used to refer to adverse health conditions caused by medical treatment (such as unwelcome side effects
Adverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
). Can there be iatrogenic syndemics? In principle, this is possible if medical treatment or medical research is involved in creating conditions that increase the likelihood that two or more diseases come together in a population. An example of this scenario would be the use of gene splicing to unite two pathogenic agents and introducing the resulting novel organism into a population. There is a possibility that this precise event occurred, for example, during a randomized, double-blind clinical trial testing the efficacy of the prototype HIV vaccine called V520. On November 6, 2007, the pharmaceutical manufacturer Merck & Co. announced that research on the drug had been stopped because interim findings showed that there appeared to be an increased risk for HIV infection among participants in the vaccine arm of the study compared to those in the placebo group. Specifically, results showed that of the 741 volunteers in the vaccine group, 24 developed HIV infection (3.2%), while among the 762 volunteers in the placebo arm of the trial, 21 developed HIV (2.75%). Notably, investigators in the study reported a higher risk of HIV infection was found among participants who had an existing immunity to the common cold virus (known as adenovirus type 5 or Ad5). The vaccine was created using a mixture of three components, each of which was made in the laboratory with a replication-defective version of Ad5. This was the organism selected to serve as a carrier, or delivery vector, for three synthetically produced HIV genes. Researchers suggested one explanation for the higher rate of HIV infection among individuals in the treatment group was that the vaccine lowered defenses against the human immunodeficiency virus. In other words, novel organisms created through splicing of genes from two naturally occurring pathogens may have increased the rate of disease. While other explanations of the results exist, the study suggests the possibility of the emergence of syndemics with an iatrogenic origin.
Examples of syndemics
Various syndemics (although not always labeled as such) have been described in the literature already, including: the SAVA syndemic (substance abuse, violence and AIDS): the hookwormHookworm
The hookworm is a parasitic nematode that lives in the small intestine of its host, which may be a mammal such as a dog, cat, or human. Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus. A. duodenale predominates in the Middle East, North Africa, India...
, malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
and HIV/AIDS syndemic: the Chagas disease
Chagas disease
Chagas disease is a tropical parasitic disease caused by the flagellate protozoan Trypanosoma cruzi. T. cruzi is commonly transmitted to humans and other mammals by an insect vector, the blood-sucking insects of the subfamily Triatominae most commonly species belonging to the Triatoma, Rhodnius,...
, rheumatic heart disease and congestive heart failure
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
syndemic: the possible asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
and infectious disease
Infectious disease
Infectious diseases, also known as communicable diseases, contagious diseases or transmissible diseases comprise clinically evident illness resulting from the infection, presence and growth of pathogenic biological agents in an individual host organism...
syndemic: the malnutrition
Malnutrition
Malnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....
and depression
Depression (mood)
Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...
syndemic: the TB, HIV and violence
Violence
Violence is the use of physical force to apply a state to others contrary to their wishes. violence, while often a stand-alone issue, is often the culmination of other kinds of conflict, e.g...
syndemic: the whooping cough, influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
, tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
syndemic; the HIV and STD
Sexually transmitted disease
Sexually transmitted disease , also known as a sexually transmitted infection or venereal disease , is an illness that has a significant probability of transmission between humans by means of human sexual behavior, including vaginal intercourse, oral sex, and anal sex...
syndemic; the stress
Stress (medicine)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...
and obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
syndemic, and the mental health
Mental health
Mental health describes either a level of cognitive or emotional well-being or an absence of a mental disorder. From perspectives of the discipline of positive psychology or holism mental health may include an individual's ability to enjoy life and procure a balance between life activities and...
and HIV/AIDS syndemic. Additional syndemics are being identified around the world as public health officials, researchers, and service providers begin to focus on the connections among diseases and the social context factors that foster disease concentration and interactions. In January 2006, in a speech at the Enhancing the Healing Environment conference hosted by The Prince's Foundation for the Built Environment and The King's Fund, St James's Palace, London, Prince Charles, The Prince of Wales, noted the importance of paying attention to the built environment, physical inactivity and the obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
/diabetes syndemic.
Syndemics in history
While the rate at which new syndemics develop has accelerated through human history, as populations became larger and ever wider tracts of land were inhabited, as the speed of transportation increased with new technologies, and as human impact on the Earth's climatic and other environmental systems increased, syndemics are not a new phenomenon. An example of a syndemic from the 19th century can be found on the reservations on which Native Americans were confined with the closing of the U.S. frontier.It is estimated that in 1860 there were well over 10 million bison
Bison
Members of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...
living on the American Plains
Great Plains
The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...
. By the early 1880s, the last of the great herds of bison upon which Plains Indian peoples like the Sioux
Sioux
The Sioux are Native American and First Nations people in North America. The term can refer to any ethnic group within the Great Sioux Nation or any of the nation's many language dialects...
were dependent as a food source were gone, victims of economic greed as well as a conscious plan to control Plains Indian populations. White hunting parties scoured the region, sometimes shooting hundreds or even thousands of bison a day. At the same time, after the U.S. military's defeat at the Battle of the Little Bighorn
Battle of the Little Bighorn
The Battle of the Little Bighorn, also known as Custer's Last Stand and, by the Indians involved, as the Battle of the Greasy Grass, was an armed engagement between combined forces of Lakota, Northern Cheyenne and Arapaho people against the 7th Cavalry Regiment of the United States Army...
in 1876, there was a concerted effort to beat the Sioux into total submission. Thus, in 1872, Secretary of the Interior Columbus Delano
Columbus Delano
Columbus Delano, was a lawyer and a statesman and a member of the prominent Delano family.At the age of eight, Columbus Delano's family moved to Mount Vernon in Knox County, Ohio, a place he would call home for the rest of his life. After completing his primary education, he studied law and was...
stated: “as they become convinced that they can no longer rely upon the supply of game for their support, they will return to the more reliable source of subsistence [i.e., farming]." As a result, they were forced to give up their struggle for an independent existence on their own lands and take up reservation life at the mercy of government authority. Treaties that were signed with the Sioux in 1868 and 1876 stipulated that they would be provided with government annuities and provisions in payment for sections of their land and with the expectation among federal representatives that the Sioux would become farmers on individually held plots of land. The Sioux found themselves confined on a series of small reservations where they were treated as a conquered people. Moreover, as was typical of treaties with Native peoples, the government reneged on its promises. The food that was provided to the Sioux was insufficient and of low quality. Black Elk
Black Elk
Heȟáka Sápa was a famous Wičháša Wakȟáŋ of the Oglala Lakota . He was Heyoka and a second cousin of Crazy Horse.-Life:...
, a noted Sioux folk healer, told his biographer: “There was hunger among my people before I went across the big water [to Europe in 1886], because the Wasichus [whites] did not give us all the food they promised in the Black Hills treaty... But it was worse when I came back [1889]. My people looked pitiful… We could not eat lies and there was nothing we could do.” Under extremely stressful conditions, and with inadequate diets, as well as being the victims of overt racism on the part of the registration agents appointed to oversee Indian reserves, the Sioux confronted exposure to infectious disease transmitted from contact with whites. While knowledge about the epidemiology of the Sioux from this period is limited, James Mooney
James Mooney
James Mooney was an American ethnographer who lived for several years among the Cherokee. He did major studies of Southeastern Indians, as well as those on the Great Plains...
, an anthropologist and representative of the Bureau of Indian Affairs
Bureau of Indian Affairs
The Bureau of Indian Affairs is an agency of the federal government of the United States within the US Department of the Interior. It is responsible for the administration and management of of land held in trust by the United States for Native Americans in the United States, Native American...
sent to investigate a possible Sioux rebellion, described the health situation on the reservation in 1896: “In 1888 their cattle had been diminished by disease. In 1889, their crops were a failure ... Thus followed epidemics of measles, grippe [influenza], and whooping cough Pertussis
Pertussis
Pertussis, also known as whooping cough , is a highly contagious bacterial disease caused by Bordetella pertussis. Symptoms are initially mild, and then develop into severe coughing fits, which produce the namesake high-pitched "whoop" sound in infected babies and children when they inhale air...
, in rapid succession and with terrible fatal results…” Similarly, the Handbook of American Indians notes, “The least hopeful conditions in this respect prevail among the Dakota [Sioux] and other tribes of the colder northern regions, where pulmonary tuberculosis and scrofula are very common… Other more common diseases, are various forms of, bronchitis… pneumonia, pleurisy
Pleurisy
Pleurisy is an inflammation of the pleura, the lining of the pleural cavity surrounding the lungs. Among other things, infections are the most common cause of pleurisy....
, and measles
Measles
Measles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...
in the young. Whooping cough is also met with.” Indian children who were removed to white boarding schools were diagnosed with a wide range of diseases, including tuberculosis, trachoma, measles, small pox, whooping cough, influenza, and pneumonia.
As these accounts suggest, it is likely that the Sioux were victims of a syndemic that combined a number of interacting infectious diseases, inadequate diet, and stressful and extremely disheartening life conditions, including, with events like the massacre at Wounded Knee
Wounded Knee Massacre
The Wounded Knee Massacre happened on December 29, 1890, near Wounded Knee Creek on the Lakota Pine Ridge Indian Reservation in South Dakota, USA. On the day before, a detachment of the U.S. 7th Cavalry Regiment commanded by Major Samuel M...
in 1890 and the murder of their leader Sitting Bull
Sitting Bull
Sitting Bull Sitting Bull Sitting Bull (Lakota: Tȟatȟáŋka Íyotake (in Standard Lakota Orthography), also nicknamed Slon-he or "Slow"; (c. 1831 – December 15, 1890) was a Hunkpapa Lakota Sioux holy man who led his people as a tribal chief during years of resistance to United States government policies...
, outright brutalization. As a result, while the official mortality rate on the reservation was between one and two percent, the death rate was probably closer to 10 percent, a devastatingly high figure.
The influenza syndemics
There were three influenzaInfluenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
pandemics during the 20th century that caused widespread illness, mortality, social disruption, and significant economic losses. These occurred in 1918, 1957, and 1968. In each case, mortality rates were determined primarily by five factors: the number of people who became infected, the virulence of the virus causing the pandemic, the speed of global spread, the underlying features and vulnerabilities of the most affected populations, and the effectiveness and timeliness of the prevention and treatment measures that were implemented. These factors unite a range of bio-social causal forces, including production, communication, and transportation technologies; the medical and public health infrastructures; the specific pathogens involved and the nature of their interactions with human hosts; and the pre-existing health status of patients. All of these, in turn, are shaped, to greater or somewhat lesser degree, by overarching political economic structures globally and locally. Epidemics, in short, including their emergence, course, and impact (and whether they become widespread pandemics that exact a sorrowful toll on life and well-being) are sculpted by the configuration of human social relationships including prevailing patterns of social inequality.
The 1957 pandemic was caused by the Asian influenza virus (known as the H2N2 strain), a novel influenza variety to which humans had not yet developed immunities. The death toll of the 1957 pandemic is estimated to have been around two million globally, with approximately 70,000 deaths in the United States. A little over a decade later, the comparatively mild Hong Kong influenza pandemic erupted due to the spread of a virus strain (H3N2) that genetically was related to the more deadly form seen in 1957. The pandemic was responsible for about one million deaths around the world, almost 34,000 of which were in the United States. In both of these pandemics, death may not have been due only to the primary viral infection, but also to secondary bacterial infections among influenza patients; in short, they were caused by a viral/bacterial syndemic (but see Chatterjee 2007).
The worst of the 20 century influenza pandemics was the 1918 outbreak, which epidemiologists estimate was responsible for the deaths of between 40-100 million people worldwide, making it one of the most deadly events in human history. More people died of the so-called Spanish flu
Spanish flu
The 1918 flu pandemic was an influenza pandemic, and the first of the two pandemics involving H1N1 influenza virus . It was an unusually severe and deadly pandemic that spread across the world. Historical and epidemiological data are inadequate to identify the geographic origin...
(caused by the H1N1 viral strain) pandemic in the single year of 1918 than during all four-years of the Black Death
Black Death
The Black Death was one of the most devastating pandemics in human history, peaking in Europe between 1348 and 1350. Of several competing theories, the dominant explanation for the Black Death is the plague theory, which attributes the outbreak to the bacterium Yersinia pestis. Thought to have...
(Bubonic plague
Bubonic plague
Plague is a deadly infectious disease that is caused by the enterobacteria Yersinia pestis, named after the French-Swiss bacteriologist Alexandre Yersin. Primarily carried by rodents and spread to humans via fleas, the disease is notorious throughout history, due to the unrivaled scale of death...
) scourge that lasted from 1347 to 1351 (although a significantly higher percentage of the world’s population died of the plague than of Spanish flu). It is estimated that between 20-40 percent of the world’s population became ill during the 1918 pandemic.
The pandemic had devastating effects as disease spread along trade and shipping routes and other corridors of human movement until it had circled the globe. In places like India, the mortality rate reached 50 per 1,000 population. Arriving during the closing phase of the World War I, the pandemic had a significant impact on mobilized national armies. Half of U.S. soldiers who died in the “Great War,” for example, were victims of influenza not of enemy bombs and bullets. It is estimated that almost ¾ of a million Americans died during the pandemic. As noted by one alarmed scientific observer at the time, “[if the pandemic continues] civilization could easily disappear from the face of the earth within a matter of a few more weeks”. In part, the death toll during the pandemic was caused by viral pneumonia characterized by extensive bleeding in the lungs resulting in suffocation. Many victims died within 48 hours of the appearance of the first symptom. In fact, it was not uncommon for people who appeared to be quite healthy in the morning to have died by sunset. Among those who survived the first several days, however, many died of secondary bacterial pneumonia. Moreover, it has been argued that countless numbers of those who expired quickly from the disease were co-infected with tuberculosis, which would explain the notable plummet in TB cases after 1918 (because so many carriers of the disease perished during the influenza pandemic). Again, as seen with the previous two 20th century global influenza outbreaks, disease interaction appears to have been critical, underlining the importance of syndemics more generally in the production of major public health crises.
Syndemics and the environment
As a result of the floral changes produced by global warming, a significant escalation is occurring in global rates of allergies and asthma. Currently, allergic diseases constitute the sixth leading cause of chronic illness in the United States, impacting the lives of 17 percent of the population. AsthmaAsthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
, characterized by episodic inflammation and narrowing of small airway passages in the lungs, affects about 8 percent of the U.S. population, but the rate of affected individuals has been steadily climbing in recent years, especially in low income, ethnic minority neighborhoods in cities. Thus, in 1980 asthma was found to affect only about three percent of the U.S. population according to the U.S. Centers for Disease Control and Prevention. Asthma among children has been increasing at an even faster pace than among adults, with the percentage of children with asthma going up from 3.6 percent in 1980 to 9 percent in 2005. Among ethnic minority populations, Puerto Ricans the rate of asthma is 125 percent higher than non-Hispanic white people and 80 percent higher than non-Hispanic black people. The asthma prevalence among American Indians, Alaska Natives and black people is 25 percent higher than white people. As is so often the case with health, including health conditions directly affected by global warming, the poor and marginalized suffer the gravest consequences.
Increases in rates of asthma have occurred despite improvements in air quality produced by the passage and enforcement of clean air legislation, such as both the Clean Air Act of 1963 and the Clean Air Act of 1990 in the United States. In other words, existing legislation and regulation have not kept pace with changing climatic conditions and their health consequences. Compounding the problem of air quality is the fact that air-borne pollens have been found to attach themselves to diesel particles from truck or other vehicular exhaust floating in the air, resulting in heightened rates of asthma in areas where busy roads bisect densely populated areas, most notably in poorer inner city areas. Research by the American Cancer Society found that a six percent increase in cardiopulmonary deaths occurs for every elevation of 10 μg/m3 in particulate matter concentration in the air. Exhaust from the burning of diesel fuel is a complex mixture of vapors, gases, and fine particles, including over 40 known pollutants like nitrogen oxide and known or suspected carcinogenic substances such as benzene, arsenic, and formaldehyde. Exposure to diesel exhaust irritates the eyes, nose, throat and lungs, causing coughs, headaches, light headedness and nausea, while causing people with allergies to be more susceptible allergy triggers like dust or pollen. Many particles in disease fuel are so tiny they are able to penetrate deep into the lungs when inhaled. Importantly, diesel fuel particles appear to have even greater immunologic effects in the presence of environmental allergens than they do alone. According Robert Pandya and co-workers who are studying the role of diesel fuel in asthma, “This immunologic evidence may help explain the epidemiologic studies indicating that children living along major trucking thoroughfares are at increased risk for asthmatic and allergic symptoms and are more likely to have objective evidence of respiratory dysfunction.”
Importantly, the damaging effects of diesel fuel pollution appears to go significantly beyond playing a synergistic role in the development of asthma. Recent research suggests that exposure to a combination of microscopic diesel fuel particles among people with high blood cholesterol (i.e., low-density lipoprotein, LDL or “bad cholesterol”) increases the risk for both heart attack and stroke significantly above levels found among those exposed to only one of these health risks. According to André Nel, Chief of Nanomedicine at the David Geffen School of Medicine at UCLA who led the study of duel exposure, “When you add one plus one, it normally totals two… But we found that adding diesel particles to cholesterol fats equals three. Their combination creates a dangerous synergy that wreaks cardiovascular havoc far beyond what's caused by the diesel or cholesterol alone.” The synergy begins when free radical molecules that are attached to diesel exhaust particles enter the body through the lungs and pass into the circulatory system. Another source of free radicals is the fatty acids that comprise LDL cholesterol, which produce free radicals during cell metabolism. Free radical molecules are highly unstable because they have an odd number of electrons in their outer ring. As a result, they react quickly with other compounds in order to “steal” an electron and gain stability. When the "victimized" molecule loses its electron, it, in turn, becomes a free radical and a chain reaction called oxidation is produced that is known to be damaging to living cells and tissues. Of interest to the Los Angeles research team was the consequences of both sources of free radical production coming into contact. Experimentation revealed that the two mechanisms worked in tandem to stimulate genes that promote cell inflammation, a primary risk for hardening and blockage of blood vessels (atherosclerosis
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
) and, as narrowed arteries collect cholesterol deposits and trigger blood clots, for heart attacks and strokes as well. Atherosclerotic cardiovascular disease is the leading cause of death in developed countries.
Mathematical modelling of syndemics
A mathematical modelMathematical model
A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used not only in the natural sciences and engineering disciplines A mathematical model is a...
is a simplified representation using mathematical language to describe natural, mechanical or social system dynamics. In the early 20th century, epidemiologists became increasingly interested in the use of mathematical modelling procedures to project possible patterns in the spread of infectious diseases, including potential outcomes of an epidemic. To achieve these goals, epidemiological modelers unite several types of information and analytic capacity, including: 1) mathematical equations and computational algorithms; 2) computer technology; 3) epidemiological knowledge about infectious disease dynamics, including information about specific pathogens and disease vectors; and 4) research data on social conditions and human behavior. Mathematical modelling in epidemiology
Mathematical modelling in epidemiology
It is possible to mathematically model the progress of most infectious diseases to discover the likely outcome of an epidemic or to help manage them by vaccination...
is now being applied to syndemics. Abu-Raddad, Patnaik, and Kublin (2006), for example, used modelling to quantify the syndemic effects of malaria and HIV in sub-Saharan Africa based on research in Kisumu, Kenya. These researchers point out that infection with HIV facilitates disease progression in individuals exposed to malaria. At the same time, immune reaction to malaria doubles the infectious level of HIV infected individual. In short, in typical syndemic fashion, each of these diseases amplifies the effects of the other. Using mathematical modelling, Abu-Raddad and co-workers found that 5% of HIV infections (or 8,500 cases of HIV since 1980) in Kisumu are the result of the higher HIV infectiousness of malaria-infected HIV patients. Additionally, their model attributed 10% of adult malaria episodes (or almost one million excess malaria infections since 1980) to the greater susceptibility of HIV infected individuals to malaria. Their model also suggests that HIV has contributed to the wider geographic spread of malaria in Africa, a process previously thought to be the consequence primarily of global warming. Other researchers (e.g., Herring and Sattenspiel 2007) also have begun to apply mathematical modelling to syndemics. Modelling offers an enormously useful tool for anticipating future syndemics, including eco-syndemic, based on information about the spread of various diseases across the planet and the consequent co-infections and disease interactions that will result.
In this regard, Jeremy Lauer and colleges (2003) have developed PopMod, a longitudinal population tool that models distinct and possibly interacting diseases. Unlike other life-table population models, PopMod is specifically designed to not assume the statistical independence of the diseases of interest. The PopMod has several intended purposes, including describing the time evolution of population health for standard demographic purposes (such as estimating healthy life expectancy in a population), and providing a standard measure of effectiveness for health interventions and cost-effectiveness analysis. PopMod is used as one of the standard tools of the World Health Organization’s (WHO
Who
Who may refer to:* Who , an English-language pronoun* who , a Unix command* Who?, one of the Five Ws in journalism- Art and entertainment :* Who? , a 1958 novel by Algis Budrys...
) CHOICE (Choosing Interventions that are Cost-Effective) program, an initiative designed to provide national health policy makers in the WHO’s 14 epidemiological sub-regions around the world with findings on a range of health intervention costs and effects.
Future research on syndemics
Medical anthropologist, epidemiologists, and clinical researchers are just beginning to understand the nature of syndemics. There is a critical need for new research in this area. Important arenas of inquiry include the following: First, there is a need for studies that examine the processes by which syndemics emerge, including the specific sets of health and social conditions that foster the occurrence of multiple epidemics in a population and how syndemics function to produce specific kinds of health outcomes in populations. Second, there is a need to better understand processes of interaction between specific diseases with each other and with health-related factors like malnutrition, structural violence, discrimination, stigmatization, and toxic environmental exposure that reflect oppressive social relationships. Specifically, there is a need to identify all of the ways, directly and indirectly, that diseases can interact and have, as a result, enhanced impact on human health. Third there is a need for the development of an eco-syndemic understanding of the ways in which global warmingGlobal warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
is contributing to the spread of diseases to new areas and to the potential for new disease interactions. Already it is clear that as a result of global warming infectious diseases such as West Nile Virus
West Nile virus
West Nile virus is a virus of the family Flaviviridae. Part of the Japanese encephalitis antigenic complex of viruses, it is found in both tropical and temperate regions. It mainly infects birds, but is known to infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, domestic...
are spreading to new places. Similarly malaria is now found in new places because it is spread by particular mosquito species that are migrating to new locations as a result of changing climates. As a consequence, diseases that did not often interact in the past---through co-infection of the same individuals within a population---may begin interacting more regularly. Finally, there is a need for a better understanding of how the public health systems and communities can best respond to and limit the health consequences of syndemics. Systems are needed to monitor the emergence of syndemics and to allow early-bird medical and public health responses designed to lessen their impact. Systematic ethno-epidemiological surveillance with populations subject to multiple social stressors must be one component of such a monitoring system. Current efforts by researchers at the CDC to expand the discussion of syndemics in public health discourse is an important step in the development of a funded research agenda that addresses these research needs. Given the nature of syndemics, this research requires a bio-cultural/social approach that attends to both clinical and social processes.
See also
- EpidemicEpidemicIn epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...
- List of Epidemics
- PandemicPandemicA pandemic is an epidemic of infectious disease that is spreading through human populations across a large region; for instance multiple continents, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic...
- EndemicEndemic (epidemiology)In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...
- Merrill SingerMerrill SingerMerrill Singer is a medical anthropologist with a dual appointment in the Department of Anthropology and the Center for Health, Intervention and Prevention, University of Connecticut. He is also a professor in the Department of Community Medicine and Health Care at the University of Connecticut...
- CoinfectionCoinfectionIn parasitology, coinfection is the term used to describe the simultaneous infection of a host by multiple pathogen species. In virology, coinfection can also refer to the simultaneous infection of a single cell by two or more virus particles...
Further reading
- Abu-Raddad, Laith, Patnaik, P., and Kublin, J 2006 Dual Infection with HIV and Malaria Fuels the Spread of Both Diseases in sub-Saharan Africa. Science 314:1603-1606.
- Acevedo, Gabriel 2008 Causal Determinism, Elective Affinities, and Syndemic Networks: An Application of Epidemiological Theory to the Study of non-Medical Phenomenon. All Academic Research. Available online at: http://www.allacademic.com//meta/p_mla_apa_research_citation/1/8/4/6/3/pages184630/p184630-1.php.
- Akksilp, Somsak, Karnkawinpong, Opart, Wattanaamornkiat, Wanpen, Viriyakitja, Daranee, Monkongdee, Patama, Sitti, Walya, Rienthong, Dhanida, Siraprapasiri,Taweesap, Wells, Charles D., Tappero, Jordan W. and Varmaet, Jay K. 2007 Antiretroviral Therapy during Tuberculosis Treatment and Marked Reduction in Death Rate of HIV-infected Patients, Thailand. Emerging Infectious Diseases 13(7). Available online at: http://www.cdc.gov/EID/content/13/7/1001.htm.
- Alisjahbana, B., van Crevel, R., Sahiratmadja, E., den Heijer, M., and Maya, A. 2006 Diabetes mellitus is strongly associated with tuberculosis in Indonesia. International Journal Tuberculosis and Lung Disease 10: 696–700.
- Baer, Hans and Singer, Merrill 2008 Global Warming and the Political Ecology of Health: Emerging Crises and Systemic Solutions. Left Coast Press.
- Baer, Hans, Singer, Merrill, and Susser, Ida 2004 Medical Anthropology and the World System. Begin & Garvey: Westport, CT.
- Bayliss, Elizabeth, Steiner, John, Fernald, Douglas, Crane, Lori, and Main, Deborah 2003 Descriptions of Barriers to Self-Care by Persons with Comorbid Chronic Diseases. Annal of Family Medicine 1(1): 15-21.
- Bastos, Francisco Inacio, Barcellos, Christovam, Lowndes, Catherine, and Friedman, Samuel 1999 Co-infection with malaria and HIV in injecting drug users in Brazil: a new challenge to public health? Addiction 94 (8): 1165–1174.
- Bennett, Elaine 2009 Understanding childhood malnutrition in a Maya village in Guatemala: A syndemic perspective. Doctoral Dissertation. Department of Anthropology, University of Connecticut.
- Bruce, D., Harper, G.and Network, A. 2011 Operating Without a Safety Net: Gay Male Adolescents and Emerging Adults' Experiences of Marginalization and Migration, and Implications for Theory of Syndemic Production of Health Disparities. Health Education and Behavior (in press).
- Brunarski, David 2011 The Increasing Threat of Syndemics and the Role of Chiropractic Care. Dynamic Chiropractic4(2):1.
- Brunner, E., Chandola, T. and Marmot, M. 2007 Prospective Effect of Job Strain on General and Central Obesity in the Whitehall II Study. American Journal of Epidemiology 165:828-837.
- Bulled, Nicola and Singer, Merrill 2011 Syringe-mediated Syndemics. AIDS and Behavior 13(6) in press.
- Burke, J., Lim, S. H., Marshal, M.. Silvestre A., Albert, S., Ostrow, D. and R. Stall, R. 2010 Longitudinal patterns of frequent drug use among HIV-positive and negative aging men who have sex with men (MSM) in the Multicenter AIDS Cohort Study (MACS). Presented at the XVIII International AIDS Conference, July 18–23. Vienna, Austria.
- Cain, K., Kanara, N., Laserson, K., Vannarith, C., Sameourn, K., Samnang, K., Qualls, M., Varma, J. 2007 The Epidemiology of HIV-associated Tuberculosis in Rural Cambodia. International Journal of Tuberculosis and Lung Disease 11 (9): 1008-1013.
- Cain, Kevin, Anekthananon, Thanomsak, Burapat, Channawong, Akksilp, Somsak, Mankhatitham, Wiroj, Srinak, Chawin, Nateniyom, Sriprapa, Sattayawuthipong, Wanchai, Tasaneeyapan, Theerawit, and Varma, Jay 2009 Causes of Death in HIV-infected Persons Who Have Tuberculosis, Thailand. Emerging Infectious Diseases 15(2). Available from http://www.cdc.gov/EID/content/15/2/258.htm
- Candib, Lucy 2007 Obesity and Diabetes in Vulnerable Populations: Reflection on Proximal and Distal Causes. Annals of Family Medicine 5:547-556.
- Chatterjee, R. 2007 Portrait of a Killer. ScienceNow 117(2). Available online at: http://news.sciencemag.org/sciencenow/2007/01/17-02.html.
- Chaulk, C. Patrick and Kazandjian, Vahé 2004 Moving Beyond Randomized Controlled Trials. American Journal of Public Health 94(9):1476.
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- Diedrich, C. and Flynn, J. 2011 HIV-1/Mycobacterium tuberculosis Coinfection Immunology: How Does HIV-1 Exacerbate Tuberculosis? Infection and Immunity 79(4):1407-1417.
- Easton, Delia 2004 The Urban Poor: Health Issues. Encyclopedia of Medical Anthropology, Volume 1, pp. 207–213. New York: Kluwer Academic/Plenum Publishers.
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- Engel, Jeffery 2007 Pandemic Influenza: The Critical Issues and North Carolina’s Preparedness Plan. North Carolina Medical Journal 68(1):32-37.
- Egan, James, Frye, Victoria, Kurtz, Steven, Latkin, Carl, Chen, Minxing, Tobin, Karin, Yang, Curi, and Kobtin, Beryl 2011 Migration, Neighborhoods and Networks: Approaches to Understanding How Urban Environmental Conditions Affect Syndemic Adverse Health Outcomes Among Gay, Bisexual and Other Men Who Have Sex with Men. AIDS and Behavior 15(Sup 1): 35-50.
- Everett, Margaret 2009 Diabetes Among Oaxaca’s Transnational Indigenous Population: An Emerging Syndemic. Presented at the 2009 Congress of the Latin American Studies Association, Rio de Janeiro, Brazil June 11–14, 2009. Available online at: http://lasa.international.pitt.edu/members/congress-papers/lasa2009/files/EverettMargaret.pdf.
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- Feingold, Abraham 2009 SAVA Latina: Addressing the Interplay of Substance Abuse, Violence, & AIDS Affecting Hispanic Women (Part 1). Mental Health AIDS 10(3): 4-8.
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- Freudenberg, N., Fahs, M., Galea, S., & Greenberg, A. 2006 The impact of New York City’s 1975 fiscal crisis on the tuberculosis, HIV, and homicide syndemic. American Journal of Public Health, 96(3): 424–434.
- Gerberding, J. 2005 Protecting Health — The New Research Imperative. Journal of the American Medical Association 294(11): 1403-1406.
- Gielen, A., Ghandour, R., Burke, J., Mahoney, P., McDonnell, K., and O’Campo, P. 2007 HIV/AIDS and Intimate Partner Violence: Intersecting Women’s Health Issues in the United States. Trauma, Violence and Abuse 8(2):179-198.
- González-Guarda, Rosa 2009 The Syndemic Orientation: Implications for Eliminating Hispanic Health Disparities. Hispanic Health Care International 7(3):114-115.
- González-Guarda, Rosa, McCabe, B., Florom-Smith, A., Cianelli, R., Peragallo, N. 2011 Substance Abuse, Violence, HIV, and Depression: An Underlying Syndemic Factor Among Latinas. Nursing Research (in press). [Epub ahead of print]
- Hardin, Amy, Crandall, Philip and Stankus, Tony 2011 The Zoonotic Tuberculosis Syndemic: A Literature Review and Analysis of the Scientific Journals Covering a Multidisciplinary Field That Includes Clinical Medicine, Animal Science, Wildlife Management, Bacterial Evolution, and Food Safety. Science & Technology Libraries 30(1):20-57.
- Hein, Casey and Small, Doreen 2007 Combating Diabetes, Obesity, Periodontal Disease and Interrelated Inflammatory Conditions with a Syndemic Approach. Available online at: http://www.healthdecisions.org/Dental/News/default.aspx?doc_id=109688.
- Herrick, Amy Lim, Sin, Wei, Chongyi, Smith, Helen, Guadamuz, Thomas, Friedman, Mark and Stall, Ron 2011 Resilience as an Untapped Resource in Behavioral Intervention Design for Gay Men. AIDS and Behavior DOI 10.1007/s10461-011-9895-0 (in press).
- Herring, D Ann 2008 Viral Panic, Vulnerability and the Next Pandemic. In Health, Risk and Adversity, Catherine Panter-Brick and Agustín Fuentes, Eds, pp 78–100. Oxford, U.K.: Berghahn Books, 2008.
- Herring, D. Ann and Sattenspiel, Lisa 2007 Social Contexts, Syndemics, and Infectious Disease in Northern Aboriginal Populations. American Journal of Human Biology 19:190-202.
- Himmelgreen, David, Romero-Daza, Nancy, Turkon, David, Watson, Sharon, Okello-Uma, Ipolto, and Sellen, Daniel 2009 Addressing the HIV/AIDS-food insecurity syndemic in sub-Saharan Africa. African Journal of AIDS Research 8(4):401-412.
- Himmelgreen, David and Romero-Daza, Nancy 2010 The Global Food Crisis, HIV/AIDS, and Home Gardens. Environment: Science and Policy for Sustainable Development June–July. Online at: http://www.environmentmagazine.org/Bytes%20of%20Note/Bytes-index.html.
- Iacopin, Anthony 2009 New “Syndemic” Paradigm for Interprofessional Management of Chronic Inflammatory Disease. Journal of the Canadian Dental Association 75(9): 632-633.
- Jittimanee, Sirinapha, Nateniyom, Sriprapa, Kittikraisak,Wanitchaya, Burapat, Channawong, Akksilp, Somsak, Chumpathat, Nopphanath, Sirinak, Chawin, Sattayawuthipong, Wanchai and Varma, Jay 2009 Social Stigma and Knowledge of Tuberculosis and HIV among Patients with Both Diseases in Thailand. PLoS ONE 4(7): e6360. doi:10.1371/journal.pone.0006360.
- Johnson, Roger B. 2007 Periodontitis as a Component of Hyperinflammation: Treating Periodontitis in Obese Diabetic Patients. Compendium 28(9):500-505.
- Kant, L. 2003 Diabetes Mellitus-Tuberculosis: The Brewing Double Trouble. Indian Journal of Tuberculosis 50(4): 83-84.
- Klein, H. 2011 Using a Syndemics Theory Approach to Study HIV Risk Taking in a Population of Men Who Use the Internet to Find Partners for Unprotected Sex. American Journal of Men's Health (in press).
- Kurtz, Steven 2008 Unexpected Additional Evidence For Syndemic Theory. Journal of Psychoactive Drugs 40 (4):513-521.
- Kwan, C. and Ernst, J. 2011 HIV and Tuberculosis: A Deadly Human Syndemic. Clinical Microbiology Reviews 24(2):351-376.
- Laserson, K. and Wells, C. 2007 Reaching the Targets for Tuberculosis Control: The impact of HIV. Bulletin of the World Health Organization 85(5). Available on at: http://www.scielosp.org/scielo.php?script=sci_arttext&pid=S0042-96862007000500016&lng=&nrm=iso.
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- Lim, S.H. Herrick, A., Guadamuz, T., Kao, U., Plankey, M., Ostrow, D., Shoptaw, S. and Stall, R. 2010 Childhood sexual abuse, gay-related victimization, HIV infection and syndemic productions among men who have sex with men (MSM): findings from the Multicenter AIDS Cohort Study (MACS). Presented at the XVIII International AIDS Conference, July 18–23. Vienna, Austria.
- Littleton, Juditith and Julia Park 2009 Tuberculosis and syndemics: Implications for Pacific health in New Zealand. Social Science & Medicine (11):1674-1680.
- Marshall, Mac 2005 Carolina in the Carolines: A Survey of Patterns and Meanings of Smoking on a Micronesian Island. Medical Anthropology Quarterly 19(4):354-382.
- Mavridis, Agapi 2008 Tuberculosis and Syndemics: Implications for Winnipeg, Manitoba. In Multiplying and Dividing Tuberculosis in Canada and Aotearoa New Zealand, Judith Littleton, Julie Park, Ann Herring and Tracy Farmer, Eds. Research in Anthropology and Linguistics e3: 43-53.
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- Mendenhall, Emily 2011 The VIDDA Syndemic: Distress and Diabetes in Social and Cultural Context. PhD Dissertation, Department of Anthropology, Northwestern University.
- Meyer, Jaimie, Springer, Sandra, Altice and Altice, Frederick 2011 Substance Abuse, Violence, and HIV in Women: A Literature Review of the Syndemic. Journal of Women's Health (in press).
- Mercado, Susan, Kirsten Havemann, Keiko Nakamura, Andrew Kiyu, Mojgan Sami, Roby Alampay, Ira Pedrasa, Divine Salvador, Jeerawat Na Thalang, and Tran Le Thuey 2007 Responding to the Health Vulnerabilities of the Urban Poor in the ‘New Urban Settings’ of Asia. Presented at Improving Urban Population Health Systems, sponsored by the Center for Sustainable Urban Development, July.
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- Moellera, Robert, Halkitisa, Perry, and Surrencea, Katie 2011 The Interplay of Syndemic Production and Serosorting in Drug-Using Gay and Bisexual Men. Journal of Gay & Lesbian Social Services 23(1):89-106.
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- Stall, Ron, Friedman, M.S., and Catania, J. 2007 Interacting Epidemics and Gay Men’s Health: A theory of Syndemic Production among Urban Gay Men. In Unequal Opportunity: Health Disparities Affecting Gay and Bisexual Men in the United States, Richard J. Wolitski, Ron Stall, and Ronald O. Valdiserri (Eds). Oxford: Oxford University Press.
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External links
- http://syndemic.chip.uconn.edu
- http://www.amazon.com/Introduction-Syndemics-Critical-Approach-Community/dp/0470472030/ref=sr_1_1?ie=UTF8&s=books&qid=1246594334&sr=1-1
- http://www.cdc.gov/syndemics/
- http://www.aaanet.org/publications/upload/49-7-Merrill-Singer-In-Focus.pdf
- http://syndemics.blogspot.com
- http://forio.com/resources/syndemic-2003/
- http://www.medterms.com/script/main/art.asp?articlekey=22591
- http://www.answers.com/topic/cultural-anthropology?cat=health
- http://www.cdc.gov/syndemics/pdfs/Encyclopedia.pdf
- http://www.princeofwales.gov.uk/speechesandarticles/a_speech_by_hrh_the_prince_of_wales_at_the_enhancing_the_hea_66.html
- http://aids-clinical-care.jwatch.org/cgi/content/full/2007/402/7
- http://www.healthdecisions.org/Dental/News/default.aspx?doc_id=109688
- http://www.nastad.org/Docs/Public/Publication/200772_July07Bulletin_webfinal.pdf
- http://forio.com/simulation/syndemic2003/Syndemic2003pres.pdf
- http://www.amazon.com/gp/reader/0761941169/ref=sib_dp_srch_pop?v=search-inside&keywords=syndemic
- http://www.encyclo.co.uk/define/syndemic
- http://blog.pucp.edu.pe/blog/ecosalud
- http://www.encyclo.co.uk/define/syndemic
- http://medanth.wikispaces.com/Syndemic