Health experts at a World Health Organization (WHO) conference in Geneva, Switzerland, are calling for more urgent measures to contain the spread of the H5N1, or bird flu, virus, before it mutates and spreads among humans.  In China, authorities have closed all live poultry shops in their capital, Beijing, in an effort to stop the spread of the disease.  VOA's Ernest Leong reports.

Health and veterinary officials meeting in Switzerland, say a mutated form of the current avian influenza that can spread among humans is inevitable. 

All countries need to coordinate their response to such an outbreak, says Dr. David Nabarro, UN Coordinator for avian and human influenza.

"And all of us need to have the continued high level engagement of national and international decision-makers to ensure that we get what we want in the form of resources and to unblock obstacles when they recur."

Although the impact of a human pandemic can be, in Dr. Nabarro's words, "pretty terrifying," the UN official also believes there is hope, through cooperation.

"But I am much more optimistic about the scope for international cooperation both to better address the epidemic of avian influenza, that we discussed a lot this morning, and secondly, to prepare for a pandemic."

Such a global program would require investing in veterinary services, boosting human disease surveillance, scientific cooperation on vaccine development and greater access to drug companies' existing anti-viral medication.

This raises another concern -- the cost of a global battle against bird flu.  The World Bank estimates that cost will be approximately $800 billion.

Current estimates on deaths from a human flu pandemic vary dramatically.  Dr. Nabarro says between five and as many as 150-million human fatalities is possible, but the World Health Organization, WHO for short, believes 7.4 million deaths is more realistic.

To date, more than 150-million birds, mostly chickens, have died, or been culled because of avian influenza.  Since December 2003, more than 60 infected people in Asia have died from exposure to bird flu.

China has dramatically increased its efforts to battle the spread of bird flu.  Authorities ordered all live poultry markets in the capital, Beijing, closed, and a mass culling of bird and poultry following a fresh flu outbreak in the country's northeast region.  Six million birds believed to have been exposed to avian influenza were slaughtered.

And China also reports three patients originally diagnosed with pneumonia, may have contracted avian influenza.  One of them, a nine-year-old boy, died.  Investigations continue into the cause of their illnesses.

To date, there are still no reports of human-to-human infection.