H3N2
Encyclopedia : H : H3 : H3N : H3N2
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The annual flu (also called "seasonal flu" or "human flu") kills an estimated 36,000 people in the United States each year. The annual flu vaccine is made by combining vaccines for the new versions of H1N1 and H3N2 viruses that nature produces each year. The dominant strain of annual flu in January 2006 is H3N2. Measured resistance to the standard antiviral drugs amantadine and rimantadine in H3N2 has increased from 1% in 1994 to 12% in 2003 to 91% in 2005. [Reason] [New York Times] "[C]ontemporary human H3N2 influenza viruses are now endemic in pigs in southern China and can reassort with avian H5N1 viruses in this intermediate host." [NAP online book]
Hong Kong Flu
The Hong Kong Flu strain of H3N2 evolved from H2N2 by antigenic shift and caused the Hong Kong Flu pandemic of 1968 and 1969 that killed up to 750,000. (Detailed chart of its evolution [here].) "An early-onset, severe form of influenza A (H3N2) made headlines when it claimed the lives of several children in the United States in late 2003." [NAP online book]Both the H2N2 and H3N2 pandemic strains contained Avian flu virus RNA segments. "While the pandemic human influenza viruses of 1957 (H2N2) and 1968 (H3N2) clearly arose through reassortment between human and avian viruses, the influenza virus causing the 'Spanish flu' in 1918 appears to be entirely derived from an avian source (Belshe 2005)." [Chapter Two : Avian Influenza by Timm C. Harder and Ortrud Werner] from excellent free on-line Book called Influenza Report 2006 which is a medical textbook that provides a comprehensive overview of epidemic and pandemic influenza.''
The Hong Kong Flu was a pandemic outbreak of influenza that began in Hong Kong in 1968 and spread to the United States of America that year. The outbreak ended the following year, in 1969.
The Hong Kong flu was the first known outbreak of the H3N2 strain.
Because of its similarity to the 1957 Asian Flu (which was the H2N2 strain, differing from the Hong Kong flu only in the chemical arrangement of the hemagglutinin protein as a result of antigenic shift) and possibly the subsequent accumulation of related antibodies in the affected population, the Hong Kong flu resulted in much fewer casualties than most pandemics. Casualty estimates vary: between 750,000 and two million people died of the virus worldwide (34,000 people in the United States) during the two years (1968-1969) that it was active. It was therefore the least lethal pandemic in the 20th century.
Further reading
- [Graphic] showing H3N2 mutations, amino acid by amino acid, among 207 isolates completely sequenced by the Influenza Genome Sequencing Project.
- [Influenza A (H3N2) Outbreak, Nepal]
- [Hot topic - Fujian-like strain A influenza]
- [Monitoring Antibodies for Swine Influenza H3N2 Virus]
- [Human influenza A(H3N2) activity remains widespread in many countries - update 7]
- [Human influenza A/H3N2 activity increases in many countries in central and eastern Europe - update 8]
- [Influenza A H3N2]
Sources
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