Richer Asian nations may be arming themselves to fight off a feared bird flu pandemic, but experts say such a scourge would be almost unstoppable and urged tougher action to stop the virus from spreading in poultry.

The H5N1 virus has killed nine people in Vietnam in recent weeks and health experts say they are aware of unreported outbreaks of the disease in poultry in nearby countries - all alarm bells after the World Health Organisation warned of a potential pandemic that could kill millions this winter.

Japan, Hong Kong, Thailand and China have all stocked up on drugs and stepped up their fight against the virus in poultry. Drug firms are racing to produce a super vaccine.

But experts say there is no realistic way to control the virus if it mutates and becomes capable of spreading from human-to-human.

“If the virus gets adapted to humans, no one, no place could cope with it because it is so infectious, and the mortality rate is so high,” said Leo Poon, an expert on the virus and professor of microbiology at the University of Hong Kong.

The virus made its first known jump to humans in Hong Kong in 1997, killing six people. Since late 2003, it has killed 41 in Thailand and Vietnam, or up to 75 percent of its victims.

Most victims were infected directly by birds. Only one of several suspected cases of human-to-human infections has been fairly definitely confirmed.

GOVERNMENTS ACT AGAINST LOOMING DISASTER

The WHO warned last week that the bird flu virus was now endemic in Asia and it appeared to be evolving in ways that increasingly favoured the start of a deadly human outbreak.

Faced with such a doomsday scenario, some governments have kicked into action. China has issued calls to immunise poultry, supervise markets and monitor transportation of live poultry to prevent the H5N1 virus from spreading.

Japan has stocked up enough Tamiflu, a drug that the WHO says can protect against bird flu, to treat 20 million people, but it has a population of more than 127 million.

Japan plans to ask people to refrain from travelling abroad or at home and temporarily close schools in case of an epidemic.

Thailand has approved a three-year, $104 million plan to combat the disease with education programmes, more laboratories, drugs and surgical masks. Vendors will need to pack slaughtered chicken in sealed plastic bags to minimise the risk of human exposure to the virus.

Hong Kong has enforced strict vaccination programmes for chickens and biosecurity measures for farms since 1997. It plans to double its stocks of Tamiflu, although that will only be enough for just over 5 percent of its 7 million population.

Experts still believe most nations would be helpless if the H5N1 virus becomes as easily transmittable as human flu. That could happen if the bug got into an animal, most probably a pig, and mingled with the type of influenza virus that affects people.

UP AGAINST THE DEVIL

Lo Wing-lok, an infectious disease expert in Hong Kong, said the infectivity of the H5N1 virus could far outstrip SARS, which infected about 8,000 people around the world in 2003 and killed about 800, straining healthcare systems to their limits.

While people who contracted severe acute respiratory syndrome were only infectious when they became seriously ill, a victim carrying an H5N1 virus that is well adapted to humans could be far more infectious, even while appearing to be healthy.

“It would have a very infective incubation period of up to six days before the onset of symptoms. So the person can look well and wouldn’t even know he is carrying the virus,” Lo said, adding that it would be nearly impossible to track down and isolate infected persons.

“And after the onset of symptoms, it will remain infective for a number of days, so the infectivity is rather long.”

Hampering the fight is a lack of efficient diagnostic tools and proper public health infrastructure in many places in Asia. Only a few laboratories in the region are capable of diagnosing the virus and test results take up to four days.

“We can respond very rapidly, but only if we can identify the first cluster and isolate it within two or three days. Only then is there a chance of aborting a pandemic,” Lo said.

That situation would not apply to many countries, he said.

However, most agree the best safeguard would be to nip the virus in the bud - by vaccinating poultry or, where necessary, slaughtering entire flocks.

Domestic poultry must also be shielded from wild birds, which are natural hosts of H5N1.

“Most important is to tackle it now, in poultry, that is the frontline of the war,” Poon said.