Of the 1170 serum samples collected from different cities in Guangxi, 170 (14.6%) were positive solely against EA H1, while 219 (18.8%) of the sera were positive solely for HL H3 swine virus (Table 4). Additionally, 126 (10.8%) were reactive against EA H1 and HL H3 according to the HI assay, indicating the possibility of a high frequency of coinfection, successive infection over time, and/or multiple infections by different IAV-S subtypes in the pig population. We did not test serologically for antibodies against other influenza A virus strains, our data are conservative estimates of the seroprevalence of IAV-S in the pig population.Table 4Seroprevalence of antibodies against different swine influenza virus in pigs in Guangxi from 2009 to 2013LocationSerum samplesaNo. (%) of sera positiveEA H1N1HL H3N2EA H1N1 + HL H3N2Nanning28386 (30.4)166 (58.7)45(15.9)Beihai6024 (40.0)29 (48.3)8(13.3)Fangchenggang403 (7.5)5 (12.5)1(2.5)Liuzhou10128 (27.7)17 (16.6)8(7.9)Laibin13031 (23.8)4 (3.1)2(1.5)Guilin13533 (24.4)33 (24.4)16(11.9)Hezhou6718 (26.9)17 (25.4)9(13.4)Hechi809 (11.2)3 (1.3)1(1.3)Baise606 (10.0)1 (1.7)0(0)Yulin13444 (32.8)51 (38.1)25(18.7)Guigang8014 (17.5)19 (23.8)11(13.8)Total1170296 (25.3)345 (29.5)126(10.8)aEurasian avian-like (EA) H1N1, A/swine/Guangxi/BB2/2013(H1N1); Human-like swine (HL) H3N2, A/swine/Guangxi/JGB4/2013 (H3N2)