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 endemic in birds in parts of Asia, Africa and the Middle East, they told a Bangkok conference.
"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, said in opening the three-day gathering of scientists from 40 countries. "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, it remains entrenched 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 Organisation (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 reassert and become a catastrophe for humans like it is in chickens," he said.
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. The conference will hear the latest research on vaccines for poultry and humans, although drugs for the latter are still going through various stages of licensing.
Another key issue was the lack of a new virus sharing deal after WHO-sponsored talks failed last year. Indonesia, the nation worst hit by bird flu with 97 human deaths, has held back samples since August last year. It wants guarantees from rich countries and drugmakers that poor countries will get access to affordable vaccines made from their samples.
Webster called on all sides to resolve the impasse. "We live in a global village and we must learn to share otherwise we are likely to pay the penalty for being selfish."
If and when a human vaccine is approved, the ability to make it is still woefully low, said Albert Osterhaus, a microbiologist at the Erasmus Medical Centre in the Netherlands. He said the current capacity of 400 million doses of flu vaccine would cover a fraction of the world's 6.6 billion people.
Other conference topics include the role of migratory birds as potential carriers, and strategies for detecting and containing the virus which has spread to more than 60 countries.
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.
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