BioEd Online

The World Health Organization has called for a prompt response to curb the spread of avian flu. The announcement follows reports that a potentially lethal virus has re-emerged in birds in Asia.

The last two weeks have seen a spate of outbreaks in Asian poultry, including at least one in China, two in Thailand and three in Vietnam. Tens of thousands of chickens and ducks have been slaughtered to halt the spread of the infection. No humans are thought to have been infected.

The WHO wants Asian countries to step up surveillance of poultry and humans. It is also asking authorities in newly hit countries to make samples of the virus strains that are responsible for the latest cases available to international research teams for study.

"If we can compare the viruses with each other and with those from the earlier outbreaks, we will have a much better picture of what is going on," says Shigeru Omi, head of the WHO's regional office for the Western Pacific. Such studies would confirm whether the virus has mutated into a new strain, and might guide the production of an effective vaccine.

The recent outbreaks show that the virus continues to circulate and that new cases could flare up in future, says Joseph Domenech, chief of the Animal Health Service at the UN Food and Agriculture Organization. "Eradication of the avian flu virus should be considered, at best, a long-term task," he says.

Strong hold

A study published in the Proceedings of the National Academy of Sciences¹ says that the virus is becoming more of a threat to human health. And one in Nature² suggests that it is gaining a stronger foothold among birds in Asia. Over the last six years, the disease has claimed just 23 human lives, although the fear is that a new, more virulent strain could emerge.

"There is no need for public anxiety, but it is vital that the countries affected share what they know with the international community," says Omi.

The affected Asian countries have responded promptly to the recent outbreaks. In China, more than 8,000 birds died or were slaughtered, including all chickens within a three-kilometre radius of the cases. Live poultry trade was suspended in all nearby animal markets.

And as scientists wait to see if the outbreaks have been successfully contained, human trials of a bird-flu vaccine are expected to begin. The biotechnology firms Aventis Pasteur, which has its headquarters in Lyon, France, and California-based Chiron have developed candidate vaccines. These are based on a strain known as H5N1, which was taken from a Vietnamese patient in February 2004.