The trend of V.cholerae by year and months of reporting during the study period is presented in Fig. 1. The number of cases reported gradually declined after 2005, and then increased in 2010. That is, the mean (sd) of cases reported from 2000 to 2004 and 2005 to 2010 was 11.2(8.0) and 5.1(7.4) respectively.