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Qinghai Lake H5N1 Bird Flu Amantadine Sensitive?
July 6, 2005
The discussion and phylogenetic tree in tomorrow's Nature article suggest that the H5N1 at Qinghai Lake is amantadine sensitive. Although much was made over the use of amantadine in poultry in China, the sequences at Genbank showed that the resistance markers were concentrated in Vietnam and Thailand, where all isolates had two amantadine resistant markers.
Although one of the two markers was present in some isolates from China, about 90% of the isolates were sensitive. The Nature paper does not mention amantadine sensitivity, but a phylogentic tree is pictured for the M gene, The new isolates from Qinghai, A/BH gull/QH/3/05, A/Bar headed Gs/QH/5/05, A/GBH gull/QH/2/05, A/Bar headed Gs/QH/12/05, are all clustered with two 2005 isolates from Shantou, A/Ck/ST/810/05 and A/Gs/ST/1621/05. Although none of these isolates are publicly available, two closely related isolates are available from Hong Kong, A/Pf/HK/D0028L/04 , and Hunnan, A/Dk/HN/5806/03. Both of these isolates are amantadine sensitive and the amantadine resistant isolates from Vietnam and Thailand are at the opposite end of the dendogram.
Based on the above, it would seem that the Qinghai Lake isolates, like most H5N1 in China and the rest of Asia, other than Vietnam and Thailand, is amantadine sensitive.