Human flu
Encyclopedia
Human flu is a term used to refer to influenza
cases caused by Orthomyxoviridae
that are endemic
to human populations (as opposed to infection relying upon zoonosis
). It is an arbitrary categorization scheme, and is not associated with phylogenetics
-based taxonomy
. Human flu-causing viruses can belong to any of three major influenza-causing Orthomyxoviruses — Influenza A virus
, Influenza B virus
and Influenza C virus
.
The annually updated trivalent influenza vaccine contains two hemagglutinin
(HA) surface glycoprotein components from Influenza A virus
strains and one from B influenza
.
Most human flu is a non-pandemic flu that is slightly different from the main human flus that existed in last year's flu season
period. This type of flu is also called "common flu" or "seasonal flu" or "annual flu". It causes yearly flu epidemic
s that are generally not deadly except to the very old or very young.
, H1N2
, and H3N2
are the only known Influenza A virus subtypes currently circulating among humans.
Genetic factors in distinguishing between "human flu viruses" and "avian influenza viruses" include:
"About 52 key genetic changes distinguish avian influenza strains from those that spread easily among people, according to researchers in Taiwan, who analyzed the genes of more than 400 A type flu viruses." "How many mutations would make an avian virus capable of infecting humans efficiently, or how many mutations would render an influenza virus a pandemic strain, is difficult to predict. We have examined sequences from the 1918 strain, which is the only pandemic influenza virus that could be entirely derived from avian strains. Of the 52 species-associated positions, 16 have residues typical for human strains; the others remained as avian signatures. The result supports the hypothesis that the 1918 pandemic virus is more closely related to the avian influenza A virus than are other human influenza viruses."
, cough
, sore throat
, muscle aches
, conjunctivitis
and, in severe cases, severe breathing problems and pneumonia
that may be fatal. The severity of the infection will depend to a large part on the state of the infected person's immune system
and if the victim has been exposed to the strain before, and is therefore partially immune.
All of these symptoms are characteristic of numerous infectious agents, so many that most diagnoses of human influenza technically are diagnoses of influenza-like illness
(ILI) and most cases of ILI are not due to influenza.
According to the World Health Organization
: "Every winter, tens of millions of people get the flu. Most are only ill and out of work for a week, yet the elderly are at a higher risk of death from the illness. We know the worldwide death toll exceeds a few hundred thousand people a year, but even in developed countries the numbers are uncertain, because medical authorities don't usually verify who actually died of influenza and who died of a flu-like illness."
H1N1
H2N2
H3N2
H5N1
H7N7
H1N2
H9N2
H7N2
H7N3
H10N7
s and seal
s, giving them influenza
. This limited host range is apparently responsible for the lack of Influenzavirus B caused influenza pandemics in contrast with those caused by the morphologically similar Influenzavirus A
as both mutate by both genetic drift and reassortment.
s. Yearly vaccines do not vaccinate against type C.
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...
cases caused by Orthomyxoviridae
Orthomyxoviridae
The Orthomyxoviridae are a family of RNA viruses that includes five genera: Influenzavirus A, Influenzavirus B, Influenzavirus C, Isavirus and Thogotovirus. A sixth has recently been described...
that are endemic
Endemic (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...
to human populations (as opposed to infection relying upon zoonosis
Zoonosis
A zoonosis or zoonoseis any infectious disease that can be transmitted from non-human animals to humans or from humans to non-human animals . In a study of 1415 pathogens known to affect humans, 61% were zoonotic...
). It is an arbitrary categorization scheme, and is not associated with phylogenetics
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
-based taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
. Human flu-causing viruses can belong to any of three major influenza-causing Orthomyxoviruses — Influenza A virus
Influenzavirus A
Influenza A virus causes influenza in birds and some mammals and is the only species of Influenzavirus A. Influenzavirus A is a genus of the Orthomyxoviridae family of viruses. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon...
, Influenza B virus
Influenzavirus B
Influenzavirus B is a genus in the virus family Orthomyxoviridae. The only species in this genus is called "Influenza B virus".Influenza B viruses are only known to infect humans and seals, giving them influenza...
and Influenza C virus
Influenzavirus C
Influenzavirus C is a genus in the virus family Orthomyxoviridae, which includes those viruses which cause influenza. The only species in this genus is called "Influenza C virus".Influenza C viruses are known to infect humans and pigs, giving them influenza...
.
The annually updated trivalent influenza vaccine contains two hemagglutinin
Hemagglutinin
Influenza hemagglutinin or haemagglutinin is a type of hemagglutinin found on the surface of the influenza viruses. It is an antigenic glycoprotein. It is responsible for binding the virus to the cell that is being infected...
(HA) surface glycoprotein components from Influenza A virus
Influenzavirus A
Influenza A virus causes influenza in birds and some mammals and is the only species of Influenzavirus A. Influenzavirus A is a genus of the Orthomyxoviridae family of viruses. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon...
strains and one from B influenza
Influenzavirus B
Influenzavirus B is a genus in the virus family Orthomyxoviridae. The only species in this genus is called "Influenza B virus".Influenza B viruses are only known to infect humans and seals, giving them influenza...
.
Most human flu is a non-pandemic flu that is slightly different from the main human flus that existed in last year's flu season
Flu season
Flu season is a annually-recurring time period characterized by the prevalence of outbreaks of influenza . The season occurs during the cold half of the year in each hemisphere. Influenza activity can sometimes be predicted and even tracked geographically...
period. This type of flu is also called "common flu" or "seasonal flu" or "annual flu". It causes yearly flu 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...
s that are generally not deadly except to the very old or very young.
Classification
"Human influenza virus" usually refers to those subtypes that spread widely among humans. H1N1H1N1
'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of...
, H1N2
H1N2
H1N2 is a subtype of the species Influenza A virus . It is currently pandemic in both human and pig populations.H1N1, H1N2, and H3N2 are the only known Influenza A virus subtypes currently circulating among humans....
, and H3N2
H3N2
Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
are the only known Influenza A virus subtypes currently circulating among humans.
Genetic factors in distinguishing between "human flu viruses" and "avian influenza viruses" include:
- PB2: (RNA polymeraseRNA polymeraseRNA polymerase is an enzyme that produces RNA. In cells, RNAP is needed for constructing RNA chains from DNA genes as templates, a process called transcription. RNA polymerase enzymes are essential to life and are found in all organisms and many viruses...
): Amino acidAmino acidAmino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
(or residueResidue (chemistry)In chemistry, residue is the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group. It may also refer to the undesired byproducts of a reaction....
) position 627 in the PB2 protein encoded by the PB2 RNARNARibonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
gene. Until H5N1H5N1Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...
, all known avian influenza viruses had a GluGlutamic acidGlutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...
at position 627, while all human influenza viruses had a lysineLysineLysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
. - HA: (hemagglutininHemagglutininInfluenza hemagglutinin or haemagglutinin is a type of hemagglutinin found on the surface of the influenza viruses. It is an antigenic glycoprotein. It is responsible for binding the virus to the cell that is being infected...
): Avian influenza HA bind alpha 2-3 sialic acidSialic acidSialic acid is a generic term for the N- or O-substituted derivatives of neuraminic acid, a monosaccharide with a nine-carbon backbone. It is also the name for the most common member of this group, N-acetylneuraminic acid...
receptors while human influenza HA bind alpha 2-6 sialic acid receptors. Swine influenza viruses have the ability to bind both types of sialic acid receptors.
"About 52 key genetic changes distinguish avian influenza strains from those that spread easily among people, according to researchers in Taiwan, who analyzed the genes of more than 400 A type flu viruses." "How many mutations would make an avian virus capable of infecting humans efficiently, or how many mutations would render an influenza virus a pandemic strain, is difficult to predict. We have examined sequences from the 1918 strain, which is the only pandemic influenza virus that could be entirely derived from avian strains. Of the 52 species-associated positions, 16 have residues typical for human strains; the others remained as avian signatures. The result supports the hypothesis that the 1918 pandemic virus is more closely related to the avian influenza A virus than are other human influenza viruses."
Characteristics
Human flu symptoms usually include feverFever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
, sore throat
Sore throat
A sore throat or throat pain is a common physical symptom usually caused by acute pharyngitis, or throat inflammation, though it also occurs in a number of other situations, such as post trauma and in diphtheria. It can cause mild to extreme pain....
, muscle aches
Myalgia
Myalgia means "muscle pain" and is a symptom of many diseases and disorders. The most common causes are the overuse or over-stretching of a muscle or group of muscles. Myalgia without a traumatic history is often due to viral infections...
, conjunctivitis
Conjunctivitis
Conjunctivitis refers to inflammation of the conjunctiva...
and, in severe cases, severe breathing problems and pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
that may be fatal. The severity of the infection will depend to a large part on the state of the infected person's immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
and if the victim has been exposed to the strain before, and is therefore partially immune.
All of these symptoms are characteristic of numerous infectious agents, so many that most diagnoses of human influenza technically are diagnoses of influenza-like illness
Influenza-like illness
Influenza-like illness , also known as acute respiratory infection and flu-like syndrome, is a medical diagnosis of possible influenza or other illness causing a set of common symptoms, with SARI referring to Severe Acute Respiratory Infection.Symptoms commonly include fever, shivering, chills,...
(ILI) and most cases of ILI are not due to influenza.
Impact
The annual human flu in the U.S. "results in approximately 36,000 deaths and more than 200,000 hospitalizations each year. In addition to this human toll, influenza is annually responsible for a total cost of over $10 billion in the U.S.".According to the World Health Organization
World 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...
: "Every winter, tens of millions of people get the flu. Most are only ill and out of work for a week, yet the elderly are at a higher risk of death from the illness. We know the worldwide death toll exceeds a few hundred thousand people a year, but even in developed countries the numbers are uncertain, because medical authorities don't usually verify who actually died of influenza and who died of a flu-like illness."
Known subtypes
The Influenza A virus subtypes that have been confirmed in humans, ordered by the number of known human pandemic deaths, are:- H1N1H1N1'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of...
caused "Spanish FluSpanish fluThe 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...
" and a reassortmentReassortmentReassortment is the mixing of the genetic material of a species into new combinations in different individuals. Several different processes contribute to reassortment, including assortment of chromosomes, and chromosomal crossover. It is particularly used when two similar viruses that are infecting...
caused 2009 swine flu outbreak - H2N2H2N2H2N2 is a subtype of the type influenzavirus A. H2N2 has mutated into various strains including the Asian flu strain , H3N2, and various strains found in birds...
caused "Asian Flu" - H3N2H3N2Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
caused "Hong Kong Flu" - H5N1H5N1Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...
"The Bird Flu" was the world's major influenza pandemicInfluenza pandemicAn influenza pandemic is an epidemic of an influenza virus that spreads on a worldwide scale and infects a large proportion of the human population. In contrast to the regular seasonal epidemics of influenza, these pandemics occur irregularly, with the 1918 Spanish flu the most serious pandemic in...
threat until the Swine Flu Pandemic of 2009. - H7N7H7N7H7N7 is a subtype of Influenzavirus A, a genus of Orthomyxovirus, the viruses responsible for influenza. Highly pathogenic strains and low pathogenic strains exist. H7N7 can infect humans, birds, pigs, seals, and horses in the wild; and has infected mice in laboratory studies...
has unusual zoonotic potential - H1N2H1N2H1N2 is a subtype of the species Influenza A virus . It is currently pandemic in both human and pig populations.H1N1, H1N2, and H3N2 are the only known Influenza A virus subtypes currently circulating among humans....
is currently endemic in humans and pigs - H9N2H9N2H9N2 is a subtype of the species Influenza A virus ."H9N2 influenza viruses of domestic ducks have become established in the domestic poultry of Asia. Phylogenetic and antigenic analyses of the H9N2 viruses isolated from Hong Kong markets suggest three distinct sublineages...
, H7N2H7N2H7N2 is a subtype of the species Influenza A virus .A CDC study following outbreaks of H7N2 in commercial poultry farms in western Virginia in 2002 concluded:...
, H7N3H7N3H7N3 is a subtype of the species Influenza A virus .In North America, the presence of H7N3 was confirmed at several poultry farms in British Columbia in February 2004. As of April 2004, 18 farms had been quarantined to halt the spread of the virus. Two cases of humans infected with it have been...
, H10N7H10N7H10N7 is a subtype of the species Influenza A virus . In 2004 in Egypt, H10N7 was reported for the first time in humans. It caused illness in two one-year old infants, residents of Ismaillia, Egypt; one child’s father a poultry merchant.The first reported H10N7 outbreak in the US occurred in...
.
H1N1
- H1N1H1N1'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of...
is currently endemic in both human and pig populations. A variant of H1N1H1N1'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of...
was responsible for the Spanish fluSpanish fluThe 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...
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...
that killed some 50 million to 100 million people worldwide over about a year in 1918 and 1919. Controversy arose in October, 2005, after the H1N1 genomeGenomeIn modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
was published in the journal, ScienceScience (journal)Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....
. Many fear that this information could be used for bioterrorismBioterrorismBioterrorism is terrorism involving the intentional release or dissemination of biological agents. These agents are bacteria, viruses, or toxins, and may be in a naturally occurring or a human-modified form. For the use of this method in warfare, see biological warfare.-Definition:According to the...
.
- "When he compared the 1918 virusSpanish fluThe 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...
with today's human flu viruses, Dr. Taubenberger noticed that it had alterations in just 25 to 30 of the virus's 4,400 amino acids. Those few changes turned a bird virus into a killer that could spread from person to person."
H2N2
- The Asian FluAsian fluAsian Flu may refer to:* The Asian Financial Crisis of 1997, or* Asian Flu, the H2N2 virus...
was a 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...
outbreak of H2N2H2N2H2N2 is a subtype of the type influenzavirus A. H2N2 has mutated into various strains including the Asian flu strain , H3N2, and various strains found in birds...
avian influenza that originated in ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
in 1957, spread worldwide that same year during which a influenza vaccine was developed, lasted until 1958 and caused between one and four million deaths.
H3N2
- H3N2H3N2Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
is currently endemic in both human and pig populations. It evolved from H2N2H2N2H2N2 is a subtype of the type influenzavirus A. H2N2 has mutated into various strains including the Asian flu strain , H3N2, and various strains found in birds...
by antigenic shiftAntigenic shiftAntigenic shift is the process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains...
and caused the Hong Kong FluHong Kong fluThe Hong Kong flu was a category 2 flu pandemic whose outbreak in 1968 and 1969 killed an estimated one million people worldwide. It was caused by an H3N2 strain of the influenza A virus, descended from H2N2 through antigenic shift, a genetic process in which genes from multiple subtypes reassorted...
pandemic of 1968 and 1969 that killed up to 750,000. "An early-onset, severe form of influenza A H3N2H3N2Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
made headlines when it claimed the lives of several children in the United States in late 2003."
- The dominant strain of annual flu in January 2006 is H3N2H3N2Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
. Measured resistance to the standard antiviral drugs amantadineAmantadineAmantadine is the organic compound known formally as 1-adamantylamine or 1-aminoadamantane. The molecule consists of adamantane backbone that has an amino group substituted at one of the four methyne positions. This pharmaceutical is sold under the name Symmetrel for use both as an antiviral and an...
and rimantadineRimantadineRimantadine is an orally administered antiviral drug used to treat, and in rare cases prevent, influenzavirus A infection. When taken within one to two days of developing symptoms, rimantadine can shorten the duration and moderate the severity of influenza. Both rimantadine and the similar drug...
in H3N2 has increased from 1% in 1994 to 12% in 2003 to 91% in 2005.
- "[C]ontemporary human H3N2H3N2Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
influenza viruses are now endemic in pigs in southern China and can reassort with avian H5N1H5N1Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...
viruses in this intermediate host."
H5N1
- H5N1H5N1Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...
was the world's major influenza pandemicInfluenza pandemicAn influenza pandemic is an epidemic of an influenza virus that spreads on a worldwide scale and infects a large proportion of the human population. In contrast to the regular seasonal epidemics of influenza, these pandemics occur irregularly, with the 1918 Spanish flu the most serious pandemic in...
threat until the Swine Flu Epidemic of 2009--a new strain of H1N1.
H7N7
- H7N7H7N7H7N7 is a subtype of Influenzavirus A, a genus of Orthomyxovirus, the viruses responsible for influenza. Highly pathogenic strains and low pathogenic strains exist. H7N7 can infect humans, birds, pigs, seals, and horses in the wild; and has infected mice in laboratory studies...
has unusual zoonotic potential. In 2003 in NetherlandsNetherlandsThe Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
89 people were confirmed to have H7N7 influenza virus infection following an outbreak in poultry on several farms. One death was recorded.
H1N2
- H1N2H1N2H1N2 is a subtype of the species Influenza A virus . It is currently pandemic in both human and pig populations.H1N1, H1N2, and H3N2 are the only known Influenza A virus subtypes currently circulating among humans....
is currently endemic in both human and pig populations. The new H1N2H1N2H1N2 is a subtype of the species Influenza A virus . It is currently pandemic in both human and pig populations.H1N1, H1N2, and H3N2 are the only known Influenza A virus subtypes currently circulating among humans....
strain appears to have resulted from the reassortment of the genes of the currently circulating influenza H1N1H1N1'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of...
and H3N2H3N2Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
subtypes. The hemagglutininHemagglutininInfluenza hemagglutinin or haemagglutinin is a type of hemagglutinin found on the surface of the influenza viruses. It is an antigenic glycoprotein. It is responsible for binding the virus to the cell that is being infected...
protein of the H1N2H1N2H1N2 is a subtype of the species Influenza A virus . It is currently pandemic in both human and pig populations.H1N1, H1N2, and H3N2 are the only known Influenza A virus subtypes currently circulating among humans....
virus is similar to that of the currently circulating H1N1H1N1'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of...
viruses and the neuraminidaseNeuraminidaseNeuraminidase enzymes are glycoside hydrolase enzymes that cleave the glycosidic linkages of neuraminic acids. Neuraminidase enzymes are a large family, found in a range of organisms. The most commonly known neuraminidase is the viral neuraminidase, a drug target for the prevention of the spread...
protein is similar to that of the current H3N2H3N2Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
viruses.
H9N2
- Low pathogenic avian influenza A (H9N2H9N2H9N2 is a subtype of the species Influenza A virus ."H9N2 influenza viruses of domestic ducks have become established in the domestic poultry of Asia. Phylogenetic and antigenic analyses of the H9N2 viruses isolated from Hong Kong markets suggest three distinct sublineages...
) infection was confirmed in 1999, in ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and Hong KongHong KongHong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
in two children, and in 2003 in Hong KongHong KongHong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
in one child. All three fully recovered.
H7N2
- One person in New YorkNew YorkNew York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
in 2003 and one person in VirginiaVirginiaThe Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
in 2002 were found to have serologic evidence of infection with H7N2H7N2H7N2 is a subtype of the species Influenza A virus .A CDC study following outbreaks of H7N2 in commercial poultry farms in western Virginia in 2002 concluded:...
. Both fully recovered.
H7N3
- In North AmericaNorth AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, the presence of avian influenza strain H7N3H7N3H7N3 is a subtype of the species Influenza A virus .In North America, the presence of H7N3 was confirmed at several poultry farms in British Columbia in February 2004. As of April 2004, 18 farms had been quarantined to halt the spread of the virus. Two cases of humans infected with it have been...
was confirmed at several poultry farms in British ColumbiaBritish ColumbiaBritish Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
in February 2004. As of April 2004, 18 farms had been quarantined to halt the spread of the virus. Two cases of humans with avian influenza have been confirmed in that region. "Symptoms included conjunctivitisConjunctivitisConjunctivitis refers to inflammation of the conjunctiva...
and mild influenzaInfluenzaInfluenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
-like illness." Both fully recovered.
H10N7
- In 2004 in EgyptEgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
H10N7H10N7H10N7 is a subtype of the species Influenza A virus . In 2004 in Egypt, H10N7 was reported for the first time in humans. It caused illness in two one-year old infants, residents of Ismaillia, Egypt; one child’s father a poultry merchant.The first reported H10N7 outbreak in the US occurred in...
is reported for the first time in humans. It caused illness in two infants in Egypt. One child’s father is a poultryPoultryPoultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...
merchant.
Influenzavirus B
Influenza B viruses are only known to infect humanHuman
Humans are the only living species in the Homo genus...
s and seal
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
s, giving them 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...
. This limited host range is apparently responsible for the lack of Influenzavirus B caused influenza pandemics in contrast with those caused by the morphologically similar Influenzavirus A
Influenzavirus A
Influenza A virus causes influenza in birds and some mammals and is the only species of Influenzavirus A. Influenzavirus A is a genus of the Orthomyxoviridae family of viruses. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon...
as both mutate by both genetic drift and reassortment.
Influenzavirus C
Flu due to the type C species is rare compared to types A or B, but can be severe and can cause local epidemicEpidemic
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...
s. Yearly vaccines do not vaccinate against type C.