Influenza A virus subtype H1N1

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This colorized transmission electron micrograph shows H1N1 influenza virus particles. Surface proteins on the virus particles are shown in black

Influenza A virus subtype H1N1, commonly known as the swine flu virus, is the subtype of influenza A virus that caused the H1N1 flu pandemic in 2009. An earlier H1N1 variant is also believed to have caused the 1918-1919 pandemic known as the Spanish flu.[1]

H1N1 2009 pandemic[edit | edit source]

Influenza A subtype H1N1 strains caused a small percentage of all human flu infections in 2004–2005. In June 2009, the World Health Organization (WHO) declared a new strain of swine origin as a pandemic, naming it A/H1N1pdm09. It spread worldwide and had caused about 17,000 deaths by the start of 2010. The H1N1 influenza pandemic was declared over on August 10, 2010.[2] This variant of H1N1 is now a strain found in the usual seasonal flu group. Many people now have some level of immunity to this flu virus, so it is no longer considered as much of a concern as it was during 2009-2010. H1N1 protection has been included in the annual flu vaccines for a number of years now.[2][3]

Spanish flu[edit | edit source]

The H1N1 variant that caused the 1918-1919 "Spanish flu" pandemic was also believed to have come from swine (pigs), before mutating to infect humans.[1]

Other swine flu viruses[edit | edit source]

Other strains of inflenza A that evolved from swine include:

Influenza vaccines[edit | edit source]

Annual influenza vaccines protect against different influenza A subtypes including H1N1 and H3N2, and both groups of inflenza B.[3][4]

ME/CFS[edit | edit source]

Pandemic influenza A (H1N1) infection was associated with a more than two-fold increased risk of CFS/ME. We found no indication of increased risk of CFS/ME after vaccination. Our findings are consistent with a model whereby symptomatic infection, rather than antigenic stimulation may trigger CFS/ME.[5]

Learn more[edit | edit source]

See also[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 Anhlan, Darisuren; Grundmann, Norbert; Makalowski, Wojciech; Ludwig, Stephan; Scholtissek, Christoph (January 2011). "Origin of the 1918 pandemic H1N1 influenza A virus as studied by codon usage patterns and phylogenetic analysis". RNA. 17 (1): 64–73. doi:10.1261/rna.2395211. ISSN 1355-8382. PMC 3004067. PMID 21068184.
  2. 2.0 2.1 "Swine flu (H1N1)". National Health Service. October 3, 2018. Retrieved November 11, 2021.
  3. 3.0 3.1 "Key Facts About Seasonal Flu Vaccine". Centers for Disease Control and Prevention. November 2, 2021. Retrieved November 11, 2021.
  4. "The national influenza immunisation programme 2021 to 2022" (PDF). Public Health England. August 2021.
  5. 5.0 5.1 Magnus, Per; Gunnes, Nina; Tveito, Kari; Bakken, Inger Johanne; Ghaderi, Sara; Stoltenberg, Camilla; Hornig, Mady; Lipkin, W. Ian; Trogstad, Lill (November 17, 2015). "Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is associated with pandemic influenza infection, but not with an adjuvanted pandemic influenza vaccine". Vaccine. 33 (46): 6173–6177. doi:10.1016/j.vaccine.2015.10.018. ISSN 1873-2518. PMID 26475444.