Health experts are rushing to investigate reports of a widespread flu outbreak in central Vietnam. The reports come just two weeks after a five-year-old boy in the same area was found to have avian flu.

The initial reports from the Quang Binh province say nearly 200  people are suffering from severe flu-like symptoms.

Local health experts are already in the area about four hundred kilometers south of Hanoi to investigate the possibility of a human outbreak of the avian flu.

But medical authorities have been quick to caution against panic. Peter Horvy, with the World Health Organization in Vietnam, says the actual number of illnesses may be far fewer than initially feared and those cases are not necessarily bird flu.

He says the medical teams are working overtime, going from house to house interviewing residents.

"To see if the number of people sick that was reported is true and then undertaking sampling of any people who are ill to see if there is any evidence that they have either common influenza or avian influenza," he said.

Tissue samples from sick people will be sent to a lab for testing.

For now, Dr. Horvy says, it appears there are only two possible bird flu cases in the area.

But if it turns out there are more, the WHO says an international team of health experts is ready to lend assistance.

The rush to action underscores international concern that the avian flu virus known as H5N1 poses a serious threat to humans.

If the virus mutates into a form that spreads among humans easily, it could quickly infect millions worldwide.

For now, avian flu remains a localized and fairly rare illness - only about one hundred people, all of them in Asia, have ever been diagnosed with the H5N1 virus since it first appeared in the late 1990s. It has killed nearly 60 people.

Almost all victims caught the virus from sick poultry.

The U.N.'s Food and Agriculture Organization is looking into unconfirmed reports that thousands of chickens died suddenly in southern Burma last week - possibly indicating a flu outbreak.

The Burmese government said Wednesday investigations failed to identify a single case of bird flu. Health officials there promised additional surveillance teams would continue looking into the reports.