 In June 2010 , scientists from Hong Kong reported discovery of a new swine flu virus which is a hybrid of the pandemic H1N1 virus and viruses previously found in pigs . It is the first report of a reassortment of the pandemic virus , which in humans has been slow to evolve . Nancy Cox , head of the influenza division at the U.S. Centers for Disease Control and Prevention , has said , " This particular paper is extremely interesting because it demonstrates for the first time what we had worried about at the very onset of the pandemic , and that is that this particular virus , when introduced into pigs , could reassort with the resident viruses in pigs and we would have new gene constellations . And bingo , here we are . " Pigs have been termed the mixing vessel of flu because they can be infected both by avian flu viruses , which rarely directly infect people , and by human viruses . When pigs become simultaneously infected with more than one virus , the viruses can swap genes , producing new variants which can pass to humans and sometimes spread amongst them . " Unlike the situation with birds and humans , we have a situation with pigs and humans where there 's a two @-@ way street of exchange of viruses . With pigs it 's very much a two @-@ way street " . 
