Eight prestigious Chinese medical experts claim that the cause of death of a 24-year-old Beijing man in November 2003, which was initially attributed to a SARS infection, was in fact an H5N1 bird flu infection, according to their letter published on Thursday in the New England Journal of Medicine.

China suffered from an outbreak of severe acute respiratory syndrome (SARS) in the early part of 2003.

But the letter did not specify when the medical experts performed the tests and when the man was proven to be infected with H5N1 bird flu. None of the eight scholars from well-known institutions, such as the State Key Laboratory of Pathogens and Biosecurity, and the Beijing Institute of Microbiology and Epidemiology, were available for comment on Friday.

Sources with the Ministry of Health told China Daily on Friday that they were still investigating into the case.

Roy Wadia, spokesman for the World Health Organization (WHO) Beijing office, told China Daily on Friday that it asked the ministry on Thursday evening to clarify the case.

"But no reply has been given yet," he said.

Genetic sequencing of H5N1 samples taken from the man found it could be a "mixed virus" with a lineage similar to the 1996 Guangdong goose virus, the researchers reported.

According to sources with the WHO, current outbreaks of the H5N1 virus were first recognized in early 2004.

In January 2004, Viet Nam identified H5N1 as the cause of human cases of severe respiratory disease with high fatality.

Before that, in 1997, human infections of H5N1 were reported in Hong Kong. Altogether 18 cases, including six fatalities, were reported in the first known instance of human infection with the virus.

In February 2003, two cases of H5N1 (one fatal) were confirmed in a Hong Kong family that had recently travelled to East China's Fujian Province.

Source: China Daily