At a conference under way in Ho Chi Minh City chaired by the World Health Organization (WHO) and the United Nations' Food and Agriculture Organization, the current situation of the virus is being assessed -- and many experts say the bird-flu virus has become more complex and could develop into a human virus.
WHO's Western Pacific regional director, Shigeru Omi, raised concerns. "It is now being found in animals such as cats and tigers, that were not previously considered susceptible to influenza A viruses," Omi told Reuters. "Not only that, it is more pathogenic than the strain found in Hong Kong in 1997. This suggests that the virus is evolving in ways that increasingly favor the start of a pandemic."
According to some estimates, nearly 140 million birds have been slaughtered or died in the Asian epidemic so far, and the financial cost of that loss is already up to 10 billion dollars.
Experts say the flu might never be eliminated, partly because ducks are silent carriers and open-air farms allow them to spread the disease. In Asia, ducks waddle in fields and farmyards, mixing with other animals and spreading the disease.
Officials also say the virus has proved to be highly versatile and resilient. Japanese researchers found flies with the bird-flu virus after an outbreak among chickens in Japan last year.
Omi also says the virus is more dangerous than SARS, or the Severe Acute Respiratory Syndrome. "The important thing for all of us," Omi said, "is that if the [avian flu] virus becomes highly contagious among humans, the health impact in terms of deaths and sickness will be enormous, and certainly much greater than SARS."
The UN food agency say the bird flue is expected to linger for many years and it calls for a massive effort to contain the virus before it spreads to other parts of the world. Some WHO scientists say the outbreak of a pandemic could kill millions of people worldwide.
WHO spokesperson Dick Thompson -- in an interview with RFE/RL in December -- took a more cautious outlook on a possible pandemic. "Well, there have been a little more than 40 cases in the last year," Thompson said. "There's a high-case fatality rate when we do see these cases. But what we haven't seen is the virus moving efficiently from one human to another."
Thompson added that it was too early in the virus's cycle to have a clear idea of what the fatality rate could be among humans.
Avian influenza does not normally infect species other than birds and pigs. But humans came down with the bird flu in Hong Kong in 1997, when the H5N1 strain infected 18 humans, six of whom died. Antiviral drugs are clinically effective against the avian flu, but do have some limitations. There is no vaccine available for the disease.