Beijing scientists said in a medical journal to be published Thursday that a man in mainland China died of bird flu in November 2003, two years before the communist country reported any human infections to the World Health Organization.
On Wednesday, however, the scientists asked without explanation to withdraw the report. But it was too late.
The man's death was initially thought to have been caused by SARS, the scientists wrote. That suggests some other cases attributed to SARS may have actually been the deadly H5N1 flu, and also raises questions about how candid China has been about both diseases.
"It's hard to believe that this is the only person in all of China who developed H5N1" that year, said Dr. John Treanor, a flu expert at the University of Rochester.
WHO was surprised by the report, which came not from the Chinese government but from eight scientists in a research letter the New England Journal of Medicine.
"We will formally request the Ministry of Health to clarify this," and why it has taken more than two years to come to light, said Roy Wadia, a WHO spokesman in China.
At least one scientist e-mailed the journal Wednesday morning, asking that the report be withdrawn, but it was already in print, a journal spokeswoman said. The journal said it was waiting to see whether the authors would now retract the paper.
The Beijing case does not necessarily mean the world faces any greater danger of a pandemic; bird flu does not spread easily from person to person, and nearly all human cases have involved close contact with infected poultry. But the report raises questions about the ability and willingness of scientists in China to study it.
Dr. Lindsey Baden, a New England Journal editor, said he does not know what caused the delay in reporting the case but suspects it took time for scientists to realize they had a novel H5N1 strain and to do the genetic sequencing needed to analyze it.
"It's to be praised that they are doing this kind of work and sharing it," Baden said, reports AP.
Russian officials have repeatedly declared that Israeli aviation poses a threat to the Russian military in Syria.