Avian-Like A (H1N1) Swine Influenza Virus Antibodies among Swine Farm Residents and Pigs in Southern China

Infection of human with avian-like A (H1N1) swine influenza virus (STY) occasionally occurs in China, suggesting a potential risk of cross-species transmission of the swine influenza H1N1 virus from pigs to humans, particularly to those having direct contact with pigs. A seroepidemiological study was conducted to assess the prevalence of antibodies against the avian-like A (H1N1) STY among swine farm residents and pigs in southern China to evaluate the risk of infection to swine farm workers. Hemagglutination inhibition (HI) assays revealed that 11.17% (61/546) of the sera samples from swine farm residents in southern China were positive for antibodies against the avian-like A (H1N1) STY. The difference in numbers of antibody-positive samples obtained from swine farm residents and a control group of healthy city residents was statistically significant (P = 0.031). In addition, 219 of the 1,180 serum samples from pigs were positive for the antibodies against an avian-like A (H1N1) STY, A/swine/Guangdong/SS1/2013(H1N1), as assessed by HI. The data suggest that occupational exposure of swine farm residents and veterinarians in southern China to pigs may increase their risk of acquiring avian-like A (H1N1) STY infection. According to a special pig farming model in southern China, the staff and residents are in close contact with infected pigs and may be among the first to become infected.