Friday, February 10, 2006

Qinghai Express to Nigeria

As Azerbaijan confirms H5N1 infection (long suspected) and China reports another human case, WHO has released additional information on one of the unsettling pieces of information that emerged from the Turkish outbreak (which now stands officially at 12 with 9 cases still under scrutiny). Initial analyses of the genetic sequences showed a virus that carried at least three changes, all potentially liable to make the virus more adapted to infecting humans (see our longer explanations here, here, here and here). Helen Branswell of Canadian Press now reports (no link) further examination of some additional viruses isolated in that outbreak have failed to show the same constellation of mutations, holding out hope those adaptive changes have yet to take hold in the circulating viral population.
"They're all basically the same. Nothing new and unusual,'' Michael Perdue, a scientist with the WHO's global influenza program, said from Geneva.


"That mutation just showed up in that one patient,'' said Perdue.


Genetic analysis of the viruses showed they are closely related to a group or clade of H5N1 viruses that caused a massive die-off of wild birds at a wildlife reserve last May in western China. These Qinghai Lake viruses have been found in dead wild birds in Russia, Turkey, Romania and a number of other spots in western Asia and Eastern Europe.

They are believed to be responsible for Africa's first outbreak of H5N1, in Nigeria.
The Nigerian outbreak has raised consternation at WHO and elsewhere because it represents intrusion of the virus into virgin territory, with unknown consequences. Reports are circulating that a disease resembling avian influenza had been killing birds in the north of the country for weeks before infection with H5N1 was identified in a farm in the region.
. . . Auwalu Haruna, secretary of the Kano State poultry farmers’ association, said that a similar infection, identified earlier as “fowl cholera”, has been spreading through flocks further north for the past two weeks. “The disease is spreading like wildfire,” he said.

“We have 20,000 new infections reported today, bringing the figure for infected birds to 80,000. What worsens the situation is the farmers’ movement of infected poultry, in a frantic effort to minimise losses,” he said.

Haruna and several market stall holders said that once chickens are seen to be infected, farmers are killing them and rapidly dumping them on the market in an effort to beat any future quarantine and make a quick profit.

“The announcement by the federal government of bird flu at Sambawa Farm shocked us, but we are just waiting for confirmation from the veterinary institute in Vom for our birds,” Haruna said. (AFP via Bahrain Tribune)
Xinhua is reporting three northern Nigerian farms hit by the virus, but there is no official confirmation. An article by Debora McKenzie in New Scientist on February 8 noted that the Nigerian outbreak fits a pattern:
The region affected is right beside a major wintering ground for 2 relatively common species of duck. Those ducks shared breeding grounds in Siberia last summer [2005] with birds that winter in Turkey and around the Black Sea, where the virus also appeared recently.


Furthermore, Kano is near the Hadejia-Nguru inland river delta, which is a major wintering location for Northern pintail and garganey ducks. They summer in breeding grounds across Siberia, where there were numerous outbreaks of H5N1 in poultry and wild birds last summer [2005]. Birds of those species that winter in Turkey and around the Black Sea also summered in the same places in Siberia, and migrants are thought to have carried H5N1 there.

The authoritative 1996 Atlas of Anatidae [ducks, geese and swans] Populations of Africa and Western Europe says the Northern pintail wintering in the Black Sea and Mediterranean basins "are lumped with those wintering in West Africa as a single large population." On average, 18 000 pintails winter each year at Hadejia-Nguru. Similar numbers of garganey ducks follow the same migration, and 500 000 of each species winter at nearby Lake Chad.

Some of the Northern pintail wintering now in Britain and along Europe's North Sea and Atlantic coasts also spent last summer [2005] on the same breeding grounds as the pintail that subsequently flew to the Black Sea, Turkey and West Africa. (New Scientist)
This again suggests wild birds as vectors of geographic spread. Nigeria, however, is blaming the outbreak on smugglers and illegal importers of pets and birds (Bloomberg). No evidence for this was given. In any case, spread among poultry and the disease vector to humans still seems to be terrestrial birds (domestic poultry).

At this point it does not seem feasible to stamp out the virus in Africa. It has found a new continent.