Review of Epidemiologic Investigations on Infection Sources of Indigenous Cholera Cases in Taiwan

Chia-Ling Liu, Ji-Jia Huang, Tzu-Mei Huang, Ding-Ping Liu

2010 Vol.26 NO.9

Correspondence Author: Chia-Ling Liu



No cholera epidemics have occurred in Taiwan since a severe outbreak caused by V. Cholerae serogroup O1 occurred in 1962 [1]. Although, during the period 1962-2009, several cholera infections have occurred, only a few are cluster infections and most of the reported cases are sporadic. The infection sources for most of the indigenous cholera infections occurred during the late twentieth century had been epidemiologically associated with the consumption of soft shelled turtle raised from contaminated farm ponds. However, the infection sources of indigenous cholera cases occurred during the recent five years were all unable to be identified. In order to understand the possible infection sources and relevant risk factors associated with cholera infections, we have reviewed epidemiologic investigation reports on indigenous cholera infection occurred during 1997~2009 and analyzed data from environmental surveillance in domestic areas, field investigation in foreign countries, and from relevant researches. The study found that all cholera infections occurred during the recent 12 years are sporadic except two cluster infections; elderly people and those with underlying disease, such as gastrectomy and chronic diseases, are population susceptible to cholera infection; and poor personal hygiene practices and food sanitation are important risk factors to cholera infections. The reasons why infection sources for most of the cholera cases could not be identified are partly because the recognition of infection sources for sporadic case has always been difficult and the insufficient information on food consumption during the incubation period of disease provided by patients. If physicians could keep vigilance and sensitivity over diagnosis of suspected cholera cases and promote notification efficiency, it would be useful for investigation of infection sources. Experiences from developed countries showed that the strains of toxigenic V. cholerae exist in natural environments, usually spread through the contamination of food, and cause infection in immuno-compromised hosts [2]. The study recommends that: 1. Local governments with cases occurred should strengthen health education directed at the susceptible population and the education of physicians on diagnosis and notification of suspected cases. 2. Investigators should do their best to collect detail information on food origin, food preparation, eating utensil, food storage, and eating habits of the reported cases, and health status of close contacts and neighborhood people. 3. National laboratory should establish data bank for native strains to facilitate the comparative analysis with strains from other countries. 4. Agriculture authority periodically conduct survey on environment and fishery of farm ponds; food sanitation authority routinely monitor on safety of marketed marine product; and authorities in charge of agriculture, food sanitation, and disease control should establish a channel for mutual communication and work together to assure citizen’s health and safety. 5. Department of disease control will have to collect and obtain information on environmental surveillance and risk assessment for coastal areas along Taiwan, Penghu, Kinmen, and Matzu.