ABSTRACT
<p><b>OBJECTIVE</b>To discuss the clustering of Yunnan unexplained sudden death (YUSD) in household and village.</p><p><b>METHODS</b>Fifty-two cases were found by YUSD surveillance system in 2005. Poisson distribution and beta-binomial distribution (BBD) were employed in studying the household distribution of the disease. Poisson distribution and negative binomial distribution (NBD) were employed in studying the village distribution of the disease.</p><p><b>RESULTS</b>BBD were fitted household distribution of YUSD very well (chi(2) = 0.25, P = 0.62), while Poisson distribution was consistent with it (chi(2) = 46.01, P < 0.001). And NBD were fitted village distribution of YUSD very well (chi(2) = 0.05, P = 0.58), however the consistency in Poisson distribution was not observed (chi(2) = 110.57, P < 0.001).</p><p><b>CONCLUSION</b>Household and village clustering of YUSD does exist.</p>