Out of 2384 samples, 1115 and 1361 were positive for PRRSV and TTSuV1, respectively. From the geographical distribution, PRRSV and TTSuV1 were detected from all 6 provinces, the prevalence rate was very high. This indicates that the two viruses are widely distributed in China, and it might reach the distribution equilibrium to some extent. TTSuV1 detection rate in PRRSV-positive samples was >60% in 4 provinces: Jiangxi was the highest (69.5%) and Shanghai the lowest (51.9%). In PRRSV-negative samples, the rate was >50% in 3 provinces: Jiangxi was the highest (55.1%) and Shanghai the lowest (33.6%). Among these, the overall prevalence of TTSuV1 in PRRSV positive/negative samples was 65.3% and 47.2%, respectively, and the former rate was higher than the latter. Table 1 shows that except Shandong province, the phenomenon of the prevalence rate of TTSuV1 in PRRSV-positive was higher than negative existed in each province. The results indicate that PRRSV and TTSuV1 are widely distributed in swine in China and TTSuV1 is mostly likely to have a synergistic effect with PRRSV.