The World Health Organization has asked China for more information following a report that a man may have died of bird flu two years earlier than Chinese officials reported the presence of the flu virus in their country.
News of the case appeared in a letter published this week in an American medical magazine, the New England Journal of Medicine. In the letter, a group of Chinese scientists said a 24-year-old Chinese man who died of pneumonia-like symptoms in 2003 might have died as a result of the H5N1 bird flu virus.
In their letter, the Chinese scientists say the tests of the dead man's tissue turned up positive for the bird flu virus.
At the time of his death, the man was counted among the victims of the then-prevalent SARS epidemic. For international health experts, the report this week raises the question of whether H5N1 was present in China before last year, when Chinese officials reported it for the first time.
Roy Wadia is a spokesman for the Beijing office of the World Health Organization, which has asked Chinese health authorities for more information.
"We would like to know when these tests were done, when this was found out," he said. " And if it indeed was found out in 2003, why wasn't it shared?"
The Chinese scientists who wrote the letter to the New England Journal of Medicine have since asked the publication to withdraw it, but it is not clear why. Chinese Foreign Ministry officials had no immediate comment Thursday on the letter.
Scientists say details of the 2003 case are important because they might help reveal how much the virus has changed genetically since then. They say this information could be useful in the formulation of a vaccine.
The World Health Organization says H5N1 has killed at least 130 people since reappearing in Asia in 2003. Most of the victims have contracted the disease from infected animals. However, health experts fear the virus may mutate into a form that can pass easily from human to human, possibly creating a worldwide pandemic.
The virus has already been reported, among birds and in some cases humans, in 10 nations in Asia, Europe, and Africa.