Resistance to the antiviral drug amantadine is spreading more rapidly among avian influenza viruses of H5N1 subtype in Southeast Asia than in North America, according to the study done by investigators at St. Jude Children's Research Hospital.
The St. Jude team reached this conclusion by analyzing sequence data of the so-called M2 protein of avian influenza viruses of different subtypes isolated in North America and Southeast Asia during 1991-2004; and by evaluating the frequency of drug-resistant strains. Sequence data refers to the makeup of a gene coding for a particular protein, in this case, the M2 protein. A properly functioning M2 protein is key to the virus' ability to replicate. The St. Jude researchers demonstrated that the largest proportion of Asian drug-resistant H5 and H9 avian influenza viruses occurred in China. A report on these findings appears in the current online edition of Virology.
H5 influenza viruses concern world health officials because H5N1 subtype has been spreading throughout chicken flocks and wild birds in Southeast Asia since it emerged in 1997. Between late 2003 and early 2004, outbreaks of highly pathogenic avian H5N1 influenza occurred among poultry in eight Asian countries, causing the death or destruction of tens of millions of birds. As of August 5, 2005, 112 cases of human H5N1 infection have been confirmed in Indonesia, Vietnam, Thailand and Cambodia, of which 57 were fatal, according to the World Health Organization. Humans contract H5N1 only from close contact with infected birds and only one probable human-to-human transmission was reported in Vietnam. This has so far prevented H5N1 from becoming a major threat to humans.
"However, if H5N1 variants acquire the capacity for sustained
Source:St. Jude Children's Research Hospital