In virology,<unk>  (A/H1N1) is a subtype of<unk>  A<unk> . Well known outbreaks of<unk>  strains in humans include the Spanish flu, the 1977 Russian flu pandemic and the 2009 swine flu pandemic. It is an orthomyxovirus that contains the glycoproteins hemagglutinin and neuraminidase. For this reason, they are described as<unk> , H1N2 etc., depending on the type of H or N antigens they express with metabolic synergy. Hemagglutinin causes red blood cells to clump together and binds the<unk>  to the infected cell. Neuraminidase is a type of glycoside hydrolase enzyme which helps to move the<unk>  particles through the infected cell and assist in budding from the host cells. Some strains of<unk>  are endemic in humans and cause a small fraction of all<unk> -like illness and a small fraction of all seasonal<unk> , for instance in 2004–2005. Other strains of<unk>  are endemic in pigs (swine<unk>  and in birds (avian<unk> . Its size is in diameter.
Influenza A virus subtype H1N1
Influenza A virus subtype H5N1
Influenza A virus subtype H6N1
Influenza A virus subtype H3N8
Influenza A virus subtype H5N6
SARS-CoV-2 Alpha variant
SARS-CoV-2 Beta variant
SARS-CoV-2 Iota variant