<P> The phylogenetic origin of the flu virus that caused the 2009 pandemics can be traced before 1918 . Around 1918 , the ancestral virus , of avian origin , crossed the species boundaries and infected humans as human H1N1 . The same phenomenon took place soon after in America , where the human virus was infecting pigs ; it led to the emergence of the H1N1 swine strain , which later became the classic swine flu . </P>
which animal is the carrier of the h1n1 virus
pigs