Indonesia says a dangerous strain of avian flu virus has been found in pigs there - a possible step towards a new form of the virus that could pass easily among humans.
Scientists from Indonesia's Ministry of Agriculture confirmed Saturday that the often-deadly H5N1 strain of avian flu virus had been found in pigs on the densely populated island of Java.
Officials gave few details, saying only that specimens had been forwarded to Hong Kong for further tests.
Since early 2004 the H5N1 virus has killed 52 people in Vietnam, Thailand and Cambodia. Most or all of the deaths occurred after the victims came in close contact with infected poultry.
However, the World Health Organization, has been worried that the virus might mutate into a form that can pass easily from one person to another. Because it is a new virus and humans have built up no immunity to it, the WHO says the mutated virus could become the agent of a world-wide flu pandemic.
Peter Cordingley, the WHO spokesman for the Western Pacific, responded cautiously to the Indonesian announcement, saying his organization had not yet been formally notified.
Pigs have genetic similarities to humans, and can carry both human and animal viruses. Mr. Cordingley explained that if a pig became infected with both types of virus at the same time, it could act as a "mixing vessel," creating a new strain that could become a serious threat to humans.
"The danger is heightened they will exchange genetic material and produce a completely new virus, based on H5N1 but with human elements - and that virus - and here's a very big 'if' - if that virus spreads to humans and became capable of transmitting easily between humans, then we would be approaching a pre-pandemic situation," said Peter Cordingley.
There were several lethal flu pandemics in the last century, including the so-called "Spanish Flu" in 1918 that killed an estimated 20 to 40 million people worldwide.
The H5N1 virus first appeared in Hong Kong in 1997, necessitating the slaughter of more than a million chickens. Six people who contracted the virus died.
The virus reappeared among chicken flocks in Southeast Asia in 2003, causing the culling tens of millions of birds, and the WHO has recently been warning of the potential for another deadly human pandemic.
Saturday's report of bird flu in Indonesia came as two new cases of polio were reported there. That brought the number of victims in a recent polio outbreak to eight children.
The crippling disease has been all but wiped out worldwide, but the failure of some countries to continue with vaccinations has allowed it to make a partial comeback. Indonesia had been free of polio for 10 years.
Authorities have vaccinated more than 5,000 children in West Java, with plans to cover 5,2 million across the country by month's end.