BANGKOK—The world cannot afford to be complacent about the H5N1 bird flu virus despite its failure to trigger a human pandemic four years after sweeping across most of Asia, experts and officials said on Wednesday.
The latest outbreaks in India underscored the need for constant vigilance against a virus entrenched in birds in parts of Asia, Africa and the Middle East, they told a bird flu conference in Bangkok.
"We can't afford to be complacent and say, 'Look, it hasn't happened yet among humans'," Yongyuth Yuthavong, Thailand's Minister of Science and Technology, told scientists from 40 countries attending the 3-day conference.
"It's not a problem that can be solved overnight," he said.
The virus has killed millions of chickens and ducks and despite the slaughter of millions more and vaccination campaigns, the disease remains endemic in many poultry populations.
People become infected only rarely, but the fatality rate is still high. Of the 351 human cases recorded since 2003, a total of 219 have died, according to the World Health Organization (WHO).
Although H5N1 has not yet evolved into a virus that can pass easily between humans, it could still do so, said Robert Webster, of St Jude Children's Research Hospital in Memphis.
"It is a dangerous virus and one that we cannot afford to trust. It still has the potential to reassort and become a catastrophe for humans like it is in chickens," he told the conference.
Others argue the jury is still out on whether H5N1 will trigger a global flu outbreak that could kill millions of people.
"I'm not convinced H5 really has the ability to jump into humans and cause the next pandemic," Peter Palese, a professor at the Mount Sinai School of Medicine in New York, told Reuters.
"Most of the human cases are the result of a large dose infection," he said, such as victims who come into close contact with sick birds.
"If you are a chicken it's a serious problem, but I'm not so sure it's the next pandemic strain," he said.
Scientists at the conference will hear the latest research on vaccines for humans and poultry, as well as case studies on how to monitor and control the disease.
Since H5N1 re-emerged in Asia four years ago after a 1997 outbreak in Hong Kong, hundreds of millions of dollars have been ploughed into studying and fighting it.
But answers to key questions continue to elude scientists.
"We don't really know what it takes to be transmissible and we don't know where it's coming from. Where is it hiding out?," Webster told Reuters.
His theory is that the virus comes from domestic poultry, with a reservoir in Asia and one possibly forming in Europe.
"It occasionally spills into wild birds and humans. Unless we really understand where that reservoir is, we're not going to get rid of it," he said.
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