Perhaps unsurprisingly, four of the changes resulted in the creation of genetic sequences identical to those found in a closely relatedvirus that naturally parasitises Salmonella.
Many scientists within the influenza community have a bona fide need to know the details of this research in order to protect the public, especially if they currently are working with related strains of the virus.
But what is more curious is this: the retrovirus is closely related to a free-living virus called Jaagsiekte sheep retrovirus, which causes lung cancer in sheep and goats, but not other species.
He said both cases were related, but it looked as though the men had been infected separately from animals rather than the virus being passed between people.