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Bird Flu - New season, new sequences?
January 5, 2005
>>A 16-year-old girl from southern Vietnam's Tay Ninh province was diagnosed with the H5N1 flu last week; she remains hospitalized in Ho Chi Minh City on a respirator, AFP reported today. (Her case has not yet been included in the WHO's case count.)
The two latest cases may herald a long winter in a region buffeted in 2004 by human deaths and the loss of millions of poultry from disease and culling. Six provinces in Vietnam have reported new outbreaks of H5N1 in poultry in recent weeks, according to data from the World Organization for Animal Health (OIE). At least 22,000 birds have been culled since early December to stop the disease from spreading, officials said in an AFP report.
The resurgence of avian flu in Vietnam comes at a time when many Vietnamese are looking forward to a traditional festival that includes eating poultry.<<
The three latest cases signal the start of the new avian flu season in Vietnam. These reports come almost exactly one year after reports of bird flu infections in Hanoi and coincide with reports of new avian infections. The new H5N1 sequences will be important. H5N1 was evolved each year via recombination since 2001,
In 2004 the sequences in Vietnam and Thailand were quite stable, Chicken isolates from summer infections were closely related to sequences from the beginning of the year. Similarly summer isolates in Thailand from patients or tigers were also similar to each other and earlier isolates.
However, it is now a new season with new sequences brought into the area. There have been reports of pigeon and wild bird H5N1 infections and these infections may offer new opportunities for recombination with new sequences.
The ability of the recent infections to cause serious illness does not seem to have changed dramatically. Of the three cases, one has died and two are in critical condition. The temporal association between these three cases, coupled with outbreaks in poultry flocks and the beginning of the flu season suggest there will be additional cases. Thus far there has not been evidence of efficient human to human transmission, but the sequence relationships between isolates from this season and last season may provide valuable clues on the pandemic potential of the new isolates.