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H3N2 California Origins in Nepal
Recombinomics Commentary
June 29, 2005
>> All 4 amino acid changes observed within most of these outbreak isolates are present within A/California/7/04, a variant strain selected as the H3N2 vaccine strain for the 2005–2006 influenza season. <<
The above comments from an upcoming paper of the H3N2 outbreak in Nepal in 2003 / 2004 on the amino acid changes in the HA of 26 isolates placed on deposit at GenBank, are consistent with analysis of nucleotide polymorphism which indicate the A/California/7/2004(H3N2) strain isolated September 16, 2004 in Santa Clara, California originated from the H3N2 circulating in Nepal in the spring of 2004.
The California strain began to appear at surveillance sites in the US at the beginning of 2005 and quickly spread across the country and then was found worldwide. It is the H3N2 component of the trivalent vaccine being prepared for the 2005/2006 flu season in the northern hemisphere.
The California has continued to evolve, and several strains more distant from the Fujian strain have already emerged, raising questions about the efficacy of the upcoming vaccine for next season. H3N2 has been changing rapidly, threatening to outpace human vaccine efforts.
Rapid evolution in H5N1 is also being observed throughout Asia and co-circulation of an aggress H5N1 and H3N2 in Asia is cause for concern, especially in Vietnam, Thailand, and Cambodia where there have been reported human cases of H5N1 in humans and the bird flu has become endemic to the bird populations in southeast Asia.
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