China Animal Health and Epidemiology Center, Qingdao 266032, China

The origin of the new A (H1N1) influenza virus recently emerging in North America is a hot controversial topic of significance in disease control and risk assessment. Some experts claimed that it was an un-usually mongrelized mix of human, avian and swine influenza viruses, while some others concluded that it was totally a simple re-assortment hybrid of two lineages of swine influenza viruses. Here the phylogenetic diversity of the viral PB1, PA and PB2 gene sequences using online web servers, and the results suggest that all the 8 genetic segments of the new virus were possibly from two lineages of swine influenza viruses, and one of the lineage was a mongrelized mix of human, avian and swine in-fluenza viruses emerging in the world approximately 10 years ago. Considering the recent epidemiol-ogical trends of the new virus, we believe it will spread more widely in the world and persist long in human populations. It also could spread among swine populations. The future wide spreading of the new virus may coincide the disappearance of a subtype of previous human influenza A virus.