The most complete analysis yet of the new H1N1 swine flu virus shows it must have been circulating undetected for years, most likely in pigs, Reuters cited researchers as saying today. They said it is important to start doing better surveillance of influenza viruses in pigs, as they are clearly a potential source of human pandemics. "Pigs have become a reservoir of viruses with the potential to cause significant respiratory outbreaks or even a possible pandemic in humans," the international team of researchers reported in the journal Science. "This virus might have been circulating undetected among swine herds somewhere in the world," they added. They also confirmed the odd mixture of human, pig and bird genes in the new virus, which has infected more than 11,000 people in 42 countries, and killed 86 of them. The World Health Organization is poised to declare a full pandemic of the virus, which so far causes mostly mild disease in people. A team at Britain's Cambridge University, the U.S. Centers for Disease Control and Prevention and elsewhere sequenced the genetic codes of 51 different samples of the new virus from the United States and Mexico. They confirmed what flu experts have been saying for years -- that influenza viruses can not only mutate quickly into new forms, but can swap whole segments of genetic information with other viruses, creating new versions to infect people. How this particular mixture arose is still a mystery, they said. "Several scenarios exist, including reassortment in Asia or the Americas, for the events that have lead to the genesis of the novel A(H1N1) virus," they wrote.
