Abstract: To survey the epidemics of H1, H3 subtypes of swine influenza virus in some scale pig farms in some provinces, 799 swine serum samples were collected from 28 factory pig farms on 12 cities in Guangdong, Hunan and Henan provinces. The antibodies against H1 and H3 subtypes of SIV were determined by HI assay.The results showed that the positive rate of H1 subtype antibody of pigs was between 0~83.33%, the average positive rate of pigs was 46.18% (369/799) and the positive rate of pig farms was 89.29% (25/28).The positive rate of H3 subtype antibody of pigs was between 0~100%, the average positive rate of pigs was 61.33% (490/799) and the positive rate of pig farms was 85.71% (24/28). The average positive rate of H1 subtype antibody of pigs of Guangdong, Hunan and Henan provinces respectively was 48.91%, 40.26% and 50.67%, the rate of H3 subtype antibody was 58.55%, 70.78% and 78.67%.It showed that the infection of H1 and H3 subtypes of swine influenza virus was widespread in the surveyed pigs of the 3 above regions.The infection rate of H3 subtype was higher than H1 subtype.The epidemics of swine influenza varied in different region.

Key words: swine influenza; serological investigation; H1 subtype; H3 subtype; HI