London Independent 
Wednesday, July 1, 2009
It has swept across the world killing at least 300 people and infecting thousands more. Yet the swine flu pandemic might not have happened had it not been for the accidental release of the same strain of influenza virus from a research laboratory in the late 1970s, according to a new study.
Scientists investigating the genetic make-up of flu viruses have concluded there is a high probability that the H1N1 strain of influenza “A” behind the current pandemic might never have been re-introduced into the human population were it not for an accidental leak from a laboratory working on the same strain in 1977.
(ARTICLE CONTINUES BELOW)
“Careful study of the genetic origin of the  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 had been preserved since 1950. The re-emergence was probably an accidental release from a laboratory source,” according to the study published in The New England Journal of Medicine.
Shanta Zimmer and Donald Burke from the University of Pittsburgh in Pennsylvania said that influenza “A” (H1N1) disappeared completely from humans after a pandemic of another strain of flu in 1957. H1N1 was not detected in annual surveillance until an outbreak of H1N1 swine flu in January 1976 at a US Army base in Fort Dix, New Jersey.
Full story here.