Friday, July 08, 2005

Bird flu in the unfriendly skies

Those following the bird flu problem were not surprised by the two papers on migratory bird die-offs in the high profile scientific journals, Nature and Science July 6, but the Main Stream Media (MSM) treated it as big news. Apparently it is easier to visualize migratory birds flying in to San Francisco than an ill person landing at SFO.

Be that as it may, there are still some interesting things about these two papers. One is the slightly different chronologies of the Qinghai Lake outbreak. The paper in Science, by a group from Beijing, says that "[o]n May 4th, 2005, a few bird wer found dead on 'Bird Island' and by the end of June more than a thousand birds were affected." This accords with the official Chinese version. The paper from Hong Kong University in Nature has this, more extensive account:
On 30 April 2005, however, an outbreak was detected in bar-headed geese (Anser indicus) at Qinghai Lake in western China . . . , which is a protected nature reserve with no poultry farms in the vicinity.

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. By 4 May, bird mortality was more than 100 a day; by 20 May, the outbreak had spread to other islets, with some 1,500 birds dead.
Thus the die-off started earlier and was more extensive than the official Chinese version. The additional detail and specificity argues for the Hong Kong account being more accurate, but at this point we have no way of knowing for sure.

Genetic analysis in both papers showed that the Qinghai virus is a reassortant and carries the signature of polybasic amino acids at the HA cleavage site typical of highly pathogenic avian influenza H5N1; and also the virulence-conferring mutation in the PB2 gene first seen in Hong Kong in 1997. A third mutation, a 20 codon deletion in the neuraminidase (NA) gene, was reported in the Beijing group's paper and similarly noted to be genotype V in the Hong Kong paper (if you are interested in the meaning of some of these terms, visit the Flu Wiki Influenza Primer II and Naming Influenza Viruses entries). Both groups agreed the Qinghai virus is distinct from others, including those circulating in Vietnam and other southeast asian countries. The Beijing group speculated it originated in southern China, although it did not specify how it might have gotten to far-away Qinghai from there.

The concern highlighted in these papers and the news media relates to the possibility (really, the probability) that the virus is established in wild bird populations and will travel wherever they go. The main species victim, the bar-headed goose, is a famous long-distance and high altitude traveler capable of flying over the Himalayas to the Indian sub-continent. It should also be mentioned that Qinghai and the adjacent autonomous region of Xinjiang where confirmed H5N1 bird die-offs also occurred, are in far western China, with Xinjiang on the borders of Kazakhstan. Thus the disease is already on Europe's doorstep.

The Hong Kong group concludes by urgently asking for intensified worldwide surveillance of poultry for signs of the disease. A perfectly reasonable suggestion that might buy a few weeks. But as a preventative for global spread, probably fruitless. The poultry industry, and potentially the world's population, could be in for a rough ride.