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Influenza viruses are members of the family Orthomyxoviridae. [2] Influenza viruses A, B, C, and D represent the four antigenic types of influenza viruses. [3] Of the four antigenic types, influenza A virus is the most severe, influenza B virus is less severe but can still cause outbreaks, and influenza C virus is usually only associated with minor symptoms.
There are four different types of influenza virus: A, B, C, and D. Influenza C usually causes only mild illness while D mostly affects animals, especially cattle.
The test for this is based solely on the effect on chickens – a virus strain is highly pathogenic avian influenza (HPAI) if 75% or more of chickens die after being deliberately infected with it. The alternative classification is low pathogenic avian influenza (LPAI) which produces mild or no symptoms. [ 89 ]
Polyvalent influenza vaccine is a type of influenza vaccine that provides immunity against more than one type of antigen. [1] In the second week after receiving the flu shot, the body's immune system is triggered by the antigens so the body starts producing antibodies. These antibodies help fight against influenza viruses.
Influenza viruses A and B are estimated to have diverged from a single ancestor around 4,000 years ago, while the ancestor of influenza viruses A and B and the ancestor of influenza virus C are estimated to have diverged from a common ancestor around 8,000 years ago. [40] Outbreaks of influenza-like disease can be found throughout recorded history.
Influenza hemagglutinin (HA) or haemagglutinin [p] (British English) is a homotrimeric glycoprotein found on the surface of influenza viruses and is integral to its infectivity. Hemagglutinin is a class I fusion protein , [ 1 ] [ 2 ] having multifunctional activity as both an attachment factor and membrane fusion protein .
The spread of avian influenza in the eastern hemisphere. According to the United Nations FAO, wild water fowl likely plays a role in the avian influenza cycle and could be the initial source for AI viruses, which may be passed on through contact with resident water fowl or domestic poultry, particularly domestic ducks. A newly mutated virus ...
Influenza B and C principally infect humans, minimizing the chance that a reassortment will change its phenotype drastically. [ 3 ] In the 1940s, Maurice Hilleman discovered antigenic shift, which is important for the emergence of new viral pathogens as it is a pathway that viruses may follow to enter a new niche .