Surveillance of cholera and control measures in Putuo district of Zhoushan city in Zhejiang province,1986-2009

Objective To understand the prevalence pattern of Vibrio cholerae in Zhoushan and provide evidence for the prevention and control of cholera. Methods The surveillance of diarrhea cases and external environment/fishery products was conducted in one urban area and one fishery village with high incidences of cholera in Putuo. Results In the first 12 years (1986-1997),63 544 cases were detected for Vibrio cholerae from 74 734 registered diarrhea patients (85.03%), and 1807 were positive for cholera (2.84%). Six cases were fatal with the case fatality rate of 0.33%. The highest incidence (374.76/lakh) was observed in 1994, and the average annual incidence was 45.48/lakh. The carriage rate in close contacts was 2.58% (151/5845). The detection rate of suspected pollutants for cholera was 3.94% (119/3018). A total of 6331 environmental and food samples were detected,48 were positive (0.76%), the positive rate was 0.27% (6/2185) for water samples,1.05% (19/1803) for fishery products,1.47% (23/1569) for stool samples,774 fly samples were all negative. A total of 2125 detected strains were identified, except 1 strain of Vibrio cholerae O139 detected in shrimp, others were strains of Vibrio cholerae O1. Inaba 1d was predominant before 1990s, and Ogawa 1b was predominant after 1990s. and the biotypes of phage 48 Vibrio cholerae strains were same with epidemic strains in that year. The drug susceptibility teas of 35 Ogawa 1b strains indicated that norfloxacin was the first choice antibiotic, followed by doxycycline (sensitive), furazolidone (moderate sensitive), and the strains were resistant to penicillin. In the second 12 years (1988-2009),43 798 of 50 591 registered diarrhea patients (86.57%) and 6192 samples were detected for Vibrio cholerae, no Vibrio cholerae was detected, Conclusion The epidemic of cholera was serious in Putuo district in the first 12 years of surveillance, and during the second 12 years, zero reporting of cholera case was realized. Long-term regular surveillance of cholera was effective measure to control cholera outbreak.