Influenza A
Among other things, influenza A viruses are fashionistas. They cover themselves in an array of accessories. But instead of wearing Dolce and Gabbana, influenza prefers "H & N," aka hemagglutinin and neuraminidase. All of them exist in wild birds around the world, so they are all bird flus. But every now and then, one evolves the ability to infect other animals - Michaeleen Doucleff
image by: Alexander OBGYN - Jamison Alexander, D.O.
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Hell hath no fury like a virus scorned
We spend most of our time worrying about the influenza A strains, which include H1N1 (yes, the swine flu) and H3N2, the latter of which is a particularly nasty subtype that puts more people in the hospital than any other sort of flu. Those A strains get more attention in part because they’re more dangerous, and they’re more dangerous because they mutate faster and are more diverse. That means our annual vaccine selection tends to be wrong for the A strains more often. We only get to pick one strain per subtype—one H1N1 virus and one H3N2 virus—and with so many mutations circulating, it’s hard to pin down exactly which one will cause the most trouble.
Resources
Influenza A
Flu A virus is the most common flu virus infecting humans, animals, and birds. It is divided into subtypes, based on the nature of their surface glycoproteins, HA and NA.
Novel and Variant Influenza A Viruses
Flu viruses constantly change and mutate. Novel and variant influenza A viruses can infect and cause severe respiratory illness in humans. These influenza viruses are different from currently circulating human influenza A virus subtypes and include influenza viruses from predominantly avian and swine origin.
What's In A Flu Name? H's And N's Tell A Tale
Although influenza B can make you just as sick as A, it has never triggered a worldwide pandemic. Those have all come from the influenza A strains. All of them exist in wild birds around the world, so they are all bird flus. But every now and then, one evolves the ability to infect other animals.
Hell hath no fury like a virus scorned
We spend most of our time worrying about the influenza A strains, which include H1N1 (yes, the swine flu) and H3N2, the latter of which is a particularly nasty subtype that puts more people in the hospital than any other sort of flu. Those A strains get more attention in part because they’re more dangerous, and they’re more dangerous because they mutate faster and are more diverse.
Virus Explorer
Every year, different subtypes of influenza A viruses infect humans, causing seasonal outbreaks of flu. Sometimes, dangerous subtypes emerge, such as the 2009 H1N1 pandemic influenza, also called swine flu. This subtype had a combination of genome segments from human, avian, and swine influenza viruses.
CDC
Influenza A viruses are divided into subtypes on the basis of two proteins on the surface of the virus: hemagglutinin (HA) and neuraminidase (NA). There are 18 known HA subtypes and 11 known NA subtypes. In birds, 16 HA and 9 NA subtypes have been identified.
CERID
Influenza A and B viruses cause seasonal epidemics of diseases almost every winter. Emergence of new and diverging influenza A virus can cause pandemics.
ScienceDirect
Influenza A infection is often confused with the common cold, which may have similar signs and symptoms. Influenza A infection resembles numerous other mild febrile diseases but stands out due to cough, muscle aches, malaise, and “sudden onset”.
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