Antibodies against avian‐like A (H1N1) swine influenza virus among swine farm residents in eastern China

In 2007, the avian‐like H1N1 virus (A/swine/Zhejiang/1/07) was first isolated in pigs in China. Recently, it was reported that a 3‐year‐old boy was infected with avian‐like A (H1N1) swine influenza virus (SIV) in Jiangsu Province, China. To investigate the prevalence of avian‐like A (H1N1) SIV infection among swine farm residents in eastern China, an active influenza surveillance program was conducted on swine farms in this region from May 21, 2010 through April 22, 2012. A total of 1,162 participants were enrolled, including 1,136 persons from 48 pig farms, as well as 26 pig farm veterinarians. A total of 10.7% and 7.8% swine farm residents were positive for antibodies against avian‐like A (H1N1) SIV by HI and NT assay, respectively, using 40 as the cut‐off antibody titer. Meanwhile, all the serum samples collected from a control of healthy city residents were negative against avian‐like A (H1N1) SIV. As the difference in numbers of antibody positive samples between the swine farm residents and health city residents controls was statistically significant ( P  = 0.002), these data suggest that occupational exposure to pigs may increase swine farm residents' and veterinarians' risk of avian‐like A (H1N1) SIV infection in eastern China. This study provides the first data on avian‐like A (H1N1) SIV infections in humans in China; the potential for avian‐like A (H1N1) SIV entering the human population should also be taken into consideration. J. Med. Virol. 86:592–596, 2014 . © 2013 Wiley Periodicals, Inc.