The swine flu pandemic may have been caused by an accidental leak from a laboratory three decades ago, scientists have claimed.
An investigation into the genetic make-up of flu viruses claims the pandemic may not have occurred, had it not been for the accidental release of the same strain of influenza virus from a research lab in 1977.
The Independent reported that researchers believe this strain of the virus had been extinct in the human population for more than 20 years until it was unwittingly reintroduced by scientists.
The study in The New England Journal of Medicine said: ‘Careful study of the genetic origin of the (1977) virus showed that it was closely related to a 1950 strain, but dissimilar to influenza ‘A’ (H1N1) strains from both 1947 and 1957.
‘This finding suggested that the 1977 outbreak strain has been preserved since 1950. The re-emergence was probably an accidental release from a laboratory source.’
The strain is thought to be behind the pandemic in 1977 which began in Russia and China.
Shanta Zimmer from the University of Pittsburgh in Pennsylvania said: ‘We cannot actually pinpoint which lab had it or accidentally released it, but the re-emergence of H1N1 in 1977 made it potentially a man-made pandemic.
‘It’s a reminder that we need to be continually vigilant in terms of laboratory procedures.’
The release of the 1950s virus may have occurred after a laboratory worker became infected accidentally and then infected family and friends.
Professor John Oxford of the Royal London Hospital said the accidental release of the 1950s strain of H1N1 in 1977 is a plausible theory.