Cholera has been in existence in Sarawak for many years and since 1873 many major epidemics have occurred. The epidemics usually occur during the dry months of May, June and July and the population affected are those in coastal areas. As in other outbreaks the areas affected were those which had poor environmental sanitation, poor water supply, poor refuse disposal and indiscriminate disposal of faeces. Malays are more affected as in Peninsular Malaysia outbreaks. The classical biotype was common prior to 1961. In later years the El Tor (biotype) has been responsible for most outbreaks.