The extent of the infection with bird flu has been much wider than recognised by health officials, it was claimed today.
A new study challenges figures for infection with the H5N1 virus reported by the World Health Organisation, it has been claimed.
Writing in today’s edition of Science, Taia Wang, of Mount Sinai School of Medicine, New York, USA, said WHO’s criteria for H5N1 infection accounts only for a select few hospitalised cases that are more likely to be severe and result in poor outcomes.
It does not account for the majority of infections and its figures do not include mild or subclinical infections, she said.
Wang and colleagues carried out a meta-analysis of 20 previous studies that assessed the blood serum of more than 14,000 participants around the world.
They estimate that between one and two per cent of all those study participants actually had evidence in their blood serum of a prior H5N1 virus infection. People who have a limited amount of H5N1 antibodies in their blood serum often report no history of influenza-like symptoms.
It means that the current fatality rate of 50 to 90 per cent, which is based on WHO criteria, could well be over-estimated, she suggests.
The high death rate has sparked alarm about the risk of the virus becoming more infectious – leading to recent scientific controversy about research should be conducted into the problem.
A large-scale, standardised approach is required to determine the true rate of human H5N1 infection in the world and its fatality rate, the report concludes.
Seroevidence for H5N1 Influenza Virus Infections in Humans: A Meta-Analysis. T.T. Wang; M.K. Parides; P. Palese. Science. February 23 2012.
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