Geographical distribution of swine (Hsw1N1) and Hong Kong (H3N2) influenza virus variants in pigs in Southeast Asia.

Influenza viruses of the Hsw1N1 and H3N2 subtypes were isolated in Hong Kong from pigs originating from Hong Kong, People's Republic of China (PRC), Singapore, and Taiwan. The H3N2 isolates were from pigs from Hong Kong and PRC, whereas the Hsw1N1 isolates were from pigs from Hong Kong, PRC, Singapore and Taiwan. The hemagglutinins of the H3N2 isolates were similar to those of the earlier A/Hong Kong/1/68 and A/Port Chalmers/1/73 variants from man. The Hsw1N1 isolates were similar to the human A/New Jersey/8/76 virus. These studies extend the geographical range of Hsw1N1 influenza virus and suggest that pigs in southeast Asia, like those in North America, harbor Hsw1N1 influenza viruses. These findings underline the importance of pigs as potential reservoirs for future human pandemics by the continued isolation (in Asia) of H3N2 and Hsw1N1 influenza viruses.