Influenza virus in Asia fast developing drug resistance
avian influenza viruses in Southeast Asia are developing resistance to drugs faster than the strains found in North America, says a study done at St Jude Children's Research Hospital in Tennessee, usa.
The St Jude team analysed sequence data (refers to the makeup of gene responsible) of the m2 protein of avian influenza viruses of different subtypes isolated in North America and Southeast Asia during the year 2004. The m2 protein is crucial for the virus to replicate. The team also evaluated the frequency of strains resistant to the antiviral drug amantadine.
The researchers studied about 60 influenza viruses isolated in Southeast Asia and 74 viruses from North America that represented the h5, h6, h7 and h9 subtypes. They also examined data from the National Library of Medicine's GenBank on 408 viruses isolated from avian hosts worldwide.
The results showed there were no avian amantadine-resistant strains isolated from 1979-1983 in northeastern us and Southeast Asia. However, 31 per cent of h5 and 11 per cent of h 9 influenza viruses from Southeast Asia isolated in 2004 carried m2 mutations. Isolates of h5 and h9 subtypes from North America during that time remained sensitive to amantadine, while 16 per cent of h7 isolates were resistant to this drug.
The researchers showed the largest proportion of Asian drug-resistant h 5 and h9 avian influenza viruses occurred in China. The findings appear in the current online edition of Virology.
h5 influenza viruses cause concern to health officials because h5 n1 subtype has been spreading throughout chicken flocks and wild birds in Southeast Asia since it emerged in 1997. If h5 n1 variants acquire the capacity for human-to-human transmission, the world may face a serious pandemic, warns Robert G Webster of St Jude.
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