An influenza pandemic is likely to affect every country leaving millions dead and make more than a quarter of the world's population ill with no vaccines available until at least next March, the World Health Organization (WHO) said yesterday.
An outbreak of bird flu that has killed 32 people in Thailand and Vietnam this year is the most likely cause of an inevitable pandemic but it was not clear if it would start in the "next week or the next years", said Dr. Klaus Stohr of the WHO global influenza program.
He predicted more than a quarter of the world's estimated 6.4 billion population would fall ill from influenza.
"There are estimates that would put the number of deaths at the range between two to seven millions and the numbers of people affected will go beyond the billion because 25 to 30 percent will fall ill," he told reporters at a meeting in Bangkok of health ministers and officials from 13 Asian nations.
"An influenza pandemic would spread globally and every country would be affected," he said.
The WHO has sounded similar warnings during two waves of bird flu outbreaks across Asia that have destroyed bird stocks and infected 44 people, killing 12 in Thailand and 20 in Vietnam.
Stohr said two companies in the US were currently developing vaccines for testing but the world faced at tricky winter and spring period without any inoculations. Officials have said a vaccine would not prevent a pandemic but could save millions of lives.
"Every hundred years there has been three of four pandemics and there's no reason to believe we will be spared," he said.
"There's no date. There's going to be another pandemic, whether it happens this year or next we don't know," he said.
The Asian H5N1 strain of the virus was "certainly the most likely one that will cause the next pandemic," Stohr said.
But he said there had been no sign of the virus mutating since April -- health officials fear it would change to a form that could spread easily between humans and trigger the pandemic -- and said a vaccination program could prove effective.
At least 20 million and perhaps as many as 50 million people died in the 1918-1919 pandemic, the highest toll of any disease in the last century, and the worst of four flu pandemics since 1890.
Scientists said the disease in 1918, which also infected up to a billion people leapt to humans by mutating from bird flu.
The strain in 1918 was especially lethal for healthy young adults. Two later pandemics hit the elderly worst but the average age of those who have contracted flu in Thailand this year has been 20 and only 15 in Vietnam, Stohr said. He said nations had to use the time to get their hospitals and public information campaigns prepared.
The meeting in Bangkok follows complaints that Asian nations have not done enough to tackle the crisis and the WHO warned the disease could now be permanent in the region.
Dr. Bjorn Melgaard, of the WHO's Southeast Asia office, said officials had hoped the bird flu outbreak would be a one-off epidemic but now appeared to be a "long-term to permanent situation."
He said it could prove to be a virus "that is able to maintain its life in bird populations continuously".
In virtually all cases in Asia this year, humans have contracted bird flu from close contact with birds although one Thai woman is suspected to have caught the disease while caring for her sick child in hospital. Similar "dead-end" cases of limited transmission have been detected in humans before and officials says it did not mark the start of a human pandemic.