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Qinghai Catastrophe Looms Large as Bird Flu Migrates
July 6, 2005
>> Initially, sick bar-headed geese were recorded on a single islet that contained about 3,000 bar-headed geese as well as some brown-headed gulls (Larus brunnicephalus), great black-headed gulls (Larus ichthyaetus) and great cormorants (Phalacrocorax carbo). Clinical findings included paralysis, unusual head tilt, staggering and neck thrill - all are known features of H5N1 disease in waterfowl.
All Qinghai isolates had a Lys 627 mutation in the PB2 gene, which has been associated with increased virulence in mice4. Phylogenetic analysis of these isolates and eight other H5N1 viruses, isolated from poultry markets in Fujian, Guangdong, Hunan and Yunnan provinces during 2005, indicated that the haemagglutinin (Fig. 1a), neuraminidase and nucleoprotein (data not shown) genes of the Qinghai viruses were closely related to the H5N1 virus A/Chicken/Shantou/4231/2003 (genotype V).
However, the other five internal genes, represented by the matrix-protein gene, were closely related to H5N1 viruses isolated from domestic poultry in southern China during 2005, represented by the virus A/Chicken/Shantou/810/2005 (genotype Z)
Qinghai Lake is an important aggregation and breeding site for bar-headed geese that are distributed over central Asia6. From September, they migrate southwards to Myanmar and over the Himalayas to India, returning to Qinghai around April6. Our findings indicate that H5N1 viruses are now being transmitted between migratory birds at the lake. <<
The above comments from tomorrow's Nature suggest the upcoming months may see considerable expansion of H5N1 worldwide via migratory birds. As noted above, the genotype of the H5N1 bird flu at Qinghai Lake is unique. Usually H5N1 infection in waterfowl is asymptomatic. However, many species at Qinghai lake are dying with neurological symptoms, which are commonly associated with H5N1, especially with the more lethal versions with can replicate in laboratory mammals like mice or ferrets. These isolates also have a PB2 mutation that is associated with virulence in many influenza A subtypes. Combining that mutation with the various other mutations in the Z genotype is cause for concern.
Qinghai Lake is at the intersection of the two major flyways in Asia, extending from Alaska in North America to Eastern Europe. Although thousands of birds have died others will likely carry H5N1 to adjacent countries and continents.
The H5N1 in Qinghai has reassorted genes which indicates there will also be recombined genes, Since many species intermingle at Qinghai Lake, more dual infections are expected, leading to more genetic diversity and instability.
The Qinghai catastrophe should begin to spread in the next few weeks.
New sequences bring new problems, as the 2005 pandemic looms larger.