Influenza prevention
Encyclopedia
Influenza prevention involves taking steps that one can use to decrease their chances of contracting flu viruses, such as the Pandemic H1N1/09 virus
, responsible for the 2009 flu pandemic
.
People who contract influenza are most infective between the second and third days after infection, and infectivity lasts for around ten days. Children are much more infectious than adults and shed virus from just before they develop symptoms until two weeks after infection. The transmission of influenza can be modeled mathematically, which helps predict how the virus will spread in a population.
Influenza can be spread in three main ways:
The relative importance of these three modes of transmission is unclear, and they may all contribute to the spread of the virus. In the airborne route, the droplets that are small enough for people to inhale are 0.5 to 5 µm in diameter and inhaling just one droplet might be enough to cause an infection. Although a single sneeze releases up to 40,000 droplets, most of these droplets are quite large and will quickly settle out of the air. How long influenza survives in airborne droplets seems to be influenced by the levels of humidity
and UV radiation: with low humidity and a lack of sunlight in winter probably aiding its survival.
As the influenza virus can persist outside of the body, it can also be transmitted by contaminated surfaces such as banknotes, doorknobs, light switches and other household items. The length of time the virus will persist on a surface varies, with the virus surviving for one to two days on hard, non-porous surfaces such as plastic or metal, for about fifteen minutes from dry paper tissues, and only five minutes on skin. However, if the virus is present in mucus, this can protect it for longer periods. Avian influenza viruses can survive indefinitely when frozen. They are inactivated by heating to 56 °C (133 °F) for a minimum of 60 minutes, as well as by acids (at pH <2).
(WHO), the "main route of transmission of the pandemic influenza virus seems to be similar to seasonal influenza
, via droplets that are expelled by speaking, sneezing or coughing." One of WHO's recommendations is to "keep your distance from people who show symptoms of influenza-like illness, such as coughing and sneezing (trying to maintain a distance of about 1 metre if possible)." Other WHO recommendations are listed below.
The American Center for Disease Control and Prevention (CDC) agrees that the "spread of novel H1N1 virus is thought to occur in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing by people with influenza." The CDC also says that a person may become infected if he or she touches something with flu viruses on it "and then touches his or her eyes, nose, or mouth."
Although face mask
s might help prevent transmission when caring for the sick, there is mixed evidence on beneficial effects in the community. Smoking raises the risk of contracting influenza, as well as producing more severe disease symptoms. Thus, according to the laws of mathematical modelling of infectious diseases, smokers raise the exponential growth
rates of influenza epidemics and may indirectly be responsible for a large percentage of influenza cases.
Since influenza spreads through both aerosols and contact with contaminated surfaces, surface sanitizing may help prevent some infections. Alcohol
is an effective sanitizer against influenza viruses, while quaternary ammonium compounds
can be used with alcohol so that the sanitizing effect lasts for longer. In hospitals, quaternary ammonium compounds and bleach
are used to sanitize rooms or equipment that have been occupied by patients with influenza symptoms. At home, this can be done effectively with a diluted chlorine bleach.
During past pandemics, closing schools, churches and theaters slowed the spread of the virus but did not have a large effect on the overall death rate. It is uncertain if reducing public gatherings, by for example closing schools and workplaces, will reduce transmission since people with influenza may just be moved from one area to another; such measures would also be difficult to enforce and might be unpopular. When small numbers of people are infected, isolating the sick might reduce the risk of transmission.
As the 2009 pandemic got underway, the first vaccine to become available in the United States by mid-October 2009 was about 2.2 million doses of the weakened live-virus nasal spray formulation
. This form was not then recommended for some of the people who at highest risk of complications from flu, including pregnant women and people with asthma. The attenuated live virus
was instead suggested to be used to allow some priority groups like health care workers and healthy children 2 or older, to allow them to be vaccinated immediately. Those to whom the weakened virus might pose a heightened risk were recommended to wait for the release of killed-virus vaccines, which followed weeks to months later.
found that roughly 90% said they would be willing to avoid shopping malls, movie theaters, public transportation, and worship services for more than two weeks if health officials told them to. It also found that parents were worried about closures of schools or day care centers, with 43% saying they would lose pay or have money problems if they had to stay home a week or more because they were sick or had to care for someone. In the UK
, the government established a National Pandemic Flu Service with a hotline and website, enabling persons with symptoms to get advice or obtain drugs without first getting a prescription from a doctor.
Pandemic H1N1/09 virus
The Pandemic H1N1/09 virus is a swine origin Influenza A virus subtype H1N1 virus strain responsible for the 2009 flu pandemic. For other names see the Nomenclature section below.-Virus characteristics:...
, responsible for the 2009 flu pandemic
2009 flu pandemic
The 2009 flu pandemic was an influenza pandemic, and the second of the two pandemics involving H1N1 influenza virus , albeit in a new version...
.
Influenza transmission
Influenza can be spread in three main ways:
- by direct transmission (when an infected person sneezes mucus directly into the eyes, nose or mouth of another person);
- the airborne route (when someone inhales the aerosols produced by an infected person coughing, sneezing or spitting);
- through hand-to-eye, hand-to-nose, or hand-to-mouth transmission, either from contaminated surfaces or from direct personal contact such as a hand-shake.
The relative importance of these three modes of transmission is unclear, and they may all contribute to the spread of the virus. In the airborne route, the droplets that are small enough for people to inhale are 0.5 to 5 µm in diameter and inhaling just one droplet might be enough to cause an infection. Although a single sneeze releases up to 40,000 droplets, most of these droplets are quite large and will quickly settle out of the air. How long influenza survives in airborne droplets seems to be influenced by the levels of humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
and UV radiation: with low humidity and a lack of sunlight in winter probably aiding its survival.
As the influenza virus can persist outside of the body, it can also be transmitted by contaminated surfaces such as banknotes, doorknobs, light switches and other household items. The length of time the virus will persist on a surface varies, with the virus surviving for one to two days on hard, non-porous surfaces such as plastic or metal, for about fifteen minutes from dry paper tissues, and only five minutes on skin. However, if the virus is present in mucus, this can protect it for longer periods. Avian influenza viruses can survive indefinitely when frozen. They are inactivated by heating to 56 °C (133 °F) for a minimum of 60 minutes, as well as by acids (at pH <2).
Novel H1N1
According to the World Health OrganizationWorld Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
(WHO), the "main route of transmission of the pandemic influenza virus seems to be similar to seasonal 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...
, via droplets that are expelled by speaking, sneezing or coughing." One of WHO's recommendations is to "keep your distance from people who show symptoms of influenza-like illness, such as coughing and sneezing (trying to maintain a distance of about 1 metre if possible)." Other WHO recommendations are listed below.
The American Center for Disease Control and Prevention (CDC) agrees that the "spread of novel H1N1 virus is thought to occur in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing by people with influenza." The CDC also says that a person may become infected if he or she touches something with flu viruses on it "and then touches his or her eyes, nose, or mouth."
Infection control
Reasonably effective ways to reduce the transmission of influenza include good personal health and hygiene habits such as: not touching your eyes, nose or mouth; frequent hand washing (with soap and water, or with alcohol-based hand rubs); covering coughs and sneezes; avoiding close contact with sick people; and staying home yourself if you are sick. Avoiding spitting is also recommended.Although face mask
Face mask
Strictly, the expression face mask is tautological and means "mask", because masks by definition go on the face; but it is sometimes used to mean:*Respirator*Among divers, diving mask...
s might help prevent transmission when caring for the sick, there is mixed evidence on beneficial effects in the community. Smoking raises the risk of contracting influenza, as well as producing more severe disease symptoms. Thus, according to the laws of mathematical modelling of infectious diseases, smokers raise the exponential growth
Exponential growth
Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...
rates of influenza epidemics and may indirectly be responsible for a large percentage of influenza cases.
Since influenza spreads through both aerosols and contact with contaminated surfaces, surface sanitizing may help prevent some infections. Alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
is an effective sanitizer against influenza viruses, while quaternary ammonium compounds
Quaternary ammonium cation
Quaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure NR4+, R being an alkyl group or an aryl group. Unlike the ammonium ion and the primary, secondary, or tertiary ammonium cations, the quaternary ammonium cations are permanently charged,...
can be used with alcohol so that the sanitizing effect lasts for longer. In hospitals, quaternary ammonium compounds and bleach
Bleach
Bleach refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. Common chemical bleaches include household chlorine bleach , lye, oxygen bleach , and bleaching powder...
are used to sanitize rooms or equipment that have been occupied by patients with influenza symptoms. At home, this can be done effectively with a diluted chlorine bleach.
During past pandemics, closing schools, churches and theaters slowed the spread of the virus but did not have a large effect on the overall death rate. It is uncertain if reducing public gatherings, by for example closing schools and workplaces, will reduce transmission since people with influenza may just be moved from one area to another; such measures would also be difficult to enforce and might be unpopular. When small numbers of people are infected, isolating the sick might reduce the risk of transmission.
WHO recommendations
According to the WHO, you can decrease your chance of contracting the flu virus by taking the following steps:- Get yourself (or family members age 6 months and older) vaccinated against current strains of influenza, if possible.
- Keep your distance from people who show symptoms of influenza-like illness, such as coughing and sneezing (trying to maintain a distance of about 1 metre if possible);
- Clean your hands thoroughly with soap and water, or cleanse them with an alcohol-based hand rub on a regular basis (especially if touching surfaces that are potentially contaminated);
- Avoid touching your mouth, nose and eyes as much as possible;
- Reduce the time spent in crowded settings if possible;
- Improve airflow in your living space by opening windows;
- Practice good health habits (including adequate sleep, eating nutritious food, and keeping physically active); and
Preventing complications in children
Watch for emergency warning signs that need urgent medical attention. These warning signs include:- Fast breathing or trouble breathing
- Bluish or gray skin color
- Not drinking enough fluids
- Not urinating or no tears when crying
- Severe or persistent vomiting
- Not waking up or not interacting
- Being so irritable that the child does not want to be held
- Pain or pressure in the chest or abdomen
- Sudden dizziness
- Confusion
- Flu-like symptoms improve but then return with fever and worse cough
Vaccination against H1N1
In the 2009 pandemic, the initial demand for vaccine greatly outstripped the supply.As the 2009 pandemic got underway, the first vaccine to become available in the United States by mid-October 2009 was about 2.2 million doses of the weakened live-virus nasal spray formulation
FluMist
FluMist is a nasal spray influenza vaccine manufactured by MedImmune, Inc. that was first introduced in 2003. It was the first and the only live attenuated vaccine for influenza available outside of Europe. It is also called live attenuated influenza vaccine . In September 2009 a LAIV intranasal...
. This form was not then recommended for some of the people who at highest risk of complications from flu, including pregnant women and people with asthma. The attenuated live virus
FluMist
FluMist is a nasal spray influenza vaccine manufactured by MedImmune, Inc. that was first introduced in 2003. It was the first and the only live attenuated vaccine for influenza available outside of Europe. It is also called live attenuated influenza vaccine . In September 2009 a LAIV intranasal...
was instead suggested to be used to allow some priority groups like health care workers and healthy children 2 or older, to allow them to be vaccinated immediately. Those to whom the weakened virus might pose a heightened risk were recommended to wait for the release of killed-virus vaccines, which followed weeks to months later.
CDC recommendations
The CDC lists these as important ways to lower the risk of transmission:- Cover the nose and mouth with a tissue when coughing or sneezing. Throw tissues in the trash after use;
- Wash hands often with soap and water, especially after coughing or sneezing. Alcohol-based hand cleaners are also effective;
- Avoid touching the eyes, nose, or mouth. Germs spread this way;
- Try to avoid close contact with sick people;
- Those sick with flu-like illness are recommended to stay home for at least 24 hours after their fever is gone, except to get medical care or for other necessities. (The fever should be gone without the use of a fever-reducing medicine.) The sickened are advised to keep away from others as much as possible to avoid making others sick.
Public opinion
A survey of Americans done in late June 2009 by the Harvard School of Public HealthHarvard School of Public Health
The Harvard School of Public Health is one of the professional graduate schools of Harvard University, located in the Longwood Area of the Boston, Massachusetts neighborhood of Mission Hill, which is next to Harvard Medical School. HSPH is considered a significant school focusing on health in the...
found that roughly 90% said they would be willing to avoid shopping malls, movie theaters, public transportation, and worship services for more than two weeks if health officials told them to. It also found that parents were worried about closures of schools or day care centers, with 43% saying they would lose pay or have money problems if they had to stay home a week or more because they were sick or had to care for someone. In the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, the government established a National Pandemic Flu Service with a hotline and website, enabling persons with symptoms to get advice or obtain drugs without first getting a prescription from a doctor.
See also
- 2009 flu pandemic vaccine2009 flu pandemic vaccineThe 2009 flu pandemic vaccines are the set of influenza vaccines that have been developed to protect against the pandemic H1N1/09 virus. These vaccines either contain inactivated influenza virus, or weakened live virus that cannot cause influenza. The killed vaccine is injected, while the live...
- 2009 flu pandemic timeline2009 flu pandemic timelineThis article covers the chronology of the 2009 novel influenza A pandemic. Flag icons denote the first announcements of confirmed cases by the respective nation-states, their first deaths , and relevant sessions and announcements of the World Health...
- 2009 flu pandemic tables2009 flu pandemic tablesThis page summarises the figures from the WHO Influenza A Situation Updates issued roughly once every other day, and since 6 July from ECDC. For each country or territory, the table lists the number of confirmed cases of swine flu on the first reported day each month, and the latest figure...
- 2009 flu pandemic by country2009 flu pandemic by countryThis article deals with the status and efforts regarding the 2009 flu pandemic by country and continent/region.-Overview:As the pandemic progresses, laboratory testing and confirmation may decrease...
- InfluenzaInfluenzaInfluenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
- Influenza vaccine
- Vitamin D and influenzaVitamin D and influenzaNumerous studies link vitamin D and influenza, as well as vitamin D and respiratory infections more generally. This vitamin up-regulates genetic expression of various endogenous antimicrobial peptides , which exhibit broad-spectrum microbicidal activity against bacteria, fungi, and viruses...