posted by admin on 20/03/06
The H5N1 virus responsible for the global bird-flu outbreak has evolved into two genetically different strains, U.S. scientists reported, raising concerns of an increased risk to humans.
Researchers from the Centers for Disease Control and Prevention reported their findings at the International Conference on Emerging Infectious Diseases being held in Atlanta.
"As the virus continues its geographic expansion, it is also undergoing genetic diversity expansion," Rebecca Garten, a researcher on the study, said in a news release.
Up until now, there was only one form of H5N1, and scientists feared that could pose a risk to humans. But now that it has split into two genetically distinct forms, scientists are even more concerned that it will evolve into a form easily transmissible between humans, which could spark a pandemic. So far, the only human cases have been from direct contact with infected poultry, and most have been poultry farmers, worked in the industry or lived in close proximity to poultry.
The CDC researchers studied over 300 H5N1 virus samples taken from both avian and human sources from 2003 through the summer of 2005. The scientists found that, in 2005, a second strain of H5N1 was affecting humans in Indonesia. They concluded that the strain belonged to different subgroup of the virus that was previously not known to cause the disease in humans. The strains are similar, but different enough that the scientists likened the two strains to cousins.
H5N1 Detected in Chickens in Pakistan
Pakistan reported its first cases of H5N1 -- in chickens. The H5 type of avian influenza was detected in chickens at two farms in northwestern Pakistan last month. Tests conducted in Britain confirmed the subtype to be H5N1.
Pakistan's Agriculture Ministry said it had taken all necessary measures to stop it spreading further in the country but urged farmers to vigilant. "We are continuously watching to see whether there is another outbreak elsewhere" in Pakistan, ministry spokesman Mohammed Afzal told Geo television.
Neighboring India, Iran and mostly recently, Afghanistan, have already reported H5N1 outbreaks, but officials confirmed this was the first case in Pakistan.
Pakistan's two cases were detected at a commercial farm in Charsadda, near Peshawar, the capital of North West Frontier Province, and at a small breeder farm in the hill-resort city of Abbottabad. The ministry said the farms were quarantined, thousands of chickens slaughtered and farm workers given medical checkups and found to be free of infection.
"So far no new farm or bird has been found to be affected with the disease anywhere in the country," a ministry statement said. It urged all poultry farmers to increase the level of "bio-security" at their farms and immediately report any abnormal or high mortality among poultry.
In 2003, between three million and four million chickens were killed in Pakistan after an outbreak of the less dangerous H7N3 strain of bird flu.
Azerbaijan Human Death Toll Climbs to Five
Meanwhile, Azerbaijan's human death toll from bird flu climbed to five, bringing the number of fatalities world-wide to 103, the World Health Organization reported. (See the WHO's latest report on human cases.)
The WHO said that seven of 11 patients from Azerbaijan had tested positive for the deadly strain of bird flu in samples checked at a major laboratory in Britain. Five of the cases were fatal.
Six of the 11 cases occurred in a small settlement in southeastern Azerbaijan, the agency said. The sources of infection are still under investigation, but they possibly were feathers from dead swans collected by young women, the WHO said, most of whom were between the ages of 15 and 20 years old. "In this community, the defeathering of birds is a task usually undertaken by adolescent girls and young women," the WHO said.
On Monday, U.S. Department of Agriculture Secretary Mike Johanns and Secretary of Interior Gale Norton announced the completion of a new early warning system to detect highly pathogenic avian flu in wild migratory birds in the U.S. The interagency plan outlines five specific strategies for early detection, including: investigating disease-outbreak events in wild birds; expanding monitoring of live wild birds; monitoring hunter-killed birds; use of sentinel animals, such as backyard poultry flocks; and environmental sampling of water and bird feces.
"By intensifying our monitoring of migratory-bird populations, we increase the likelihood of early detection, which is key to controlling the spread of the virus, particularly in our domestic poultry," Mr. Johanns said in a release.
The H5N1 strain of bird flu has killed or forced the slaughter of tens of millions of chickens and ducks across Asia since 2003, and recently spread to Europe, Africa and the Middle East. Bush administration officials have increasingly warned that H5N1 could turn up in the U.S. by the end of this year.