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All Thirty Eight H5N1 Isolates from Thailand Amantadine Resistant
August 7, 2005
Thirty eight MP gene sequences from isolates in Thailand in 2004 have become available at GenBank. Previously, all of the M2 sequences at GenBank from Vietnam or Thailand contained two Amantadine resistant polymorphisms, L26I and S31N. All thirty-eight H5N1 Thailand sequences contain both polymorphisms. Thus, all public sequences of this region from isolates in Vietnam and Thailand have these two changes. The 2005 Vietnam isolates at Los Alamos only have sequences from the HA and NA genes, but Qinghai isolates from 2005 and was as isolates from four provinces in China also have sequences at GenBank and none have the two mutations. Only three isolates at GenBank have L26I, A/ruddy turnstone/Delaware/106/98(H6N2), A/Duck/Hong Kong/P185/97(H3N2), and A/swine/Scotland/410440/94(H1N2). Only the swine from Scotland has both resistant markers, providing yet another example of the isolates from Vietnam and Thailand acquiring mammalian polymorphisms (two of the three isolates with L26I are mammalian serotypes, H1 and H3, while the only isolate with both is H1N2.
These markers also further highlight differences between H5N1 in Vietnam and Thailand, which account for most of the reported human H5N1 cases, and isolates linked to migratory birds. The sequences from Qinghai Lake are available and they do not have the Amantadine resistant markers. They also contain 18 amino acid differences in HA, indicating the pandemic vaccine will not be effective against this version of H5N1.
Although human cases of H5N1 infections related to the Qinghai isolates have not been confirmed, Boxun reports indicate that such human infections have been found in Qinghai Province with additional pneumonia clusters in Tacheng, Xinjiang. As seen in the list below of the new deposits from Thailand, H5N1 can infect a large number of bird species, and the list of species is expanding as H5N1 spreads across southern Russia and northern Kazakhstan. This expanding geographical and host range of H5N1 seems likely to soon include confirmed human cases.