A total of 1452 cases of typhoid fever was notified in Singapore from 1980-9. The morbidity rates of indigenous cases showed a steady decline from 5.9 per 100,000 population in 1980 to 1.2 per 100,000 population in 1989. The mean case fatality was 0.8%. Children, adolescents and young adults were most susceptible to typhoid fever. There was no significant difference in morbidity rates between the major ethnic groups. The vast majority of indigenous cases were sporadic while outbreaks accounted for almost one third of them. Food was the main vehicle of transmission. The commonest indigenous phage types were B1, D1 and A. Antimicrobial resistance was infrequently seen. The proportion of imported cases rose from 32% in 1980 to 72% in 1989. Almost half (48.5%) of all imported cases were local residents who contracted typhoid fever while travelling in endemic countries. As imported cases assume greater importance in the epidemiology of typhoid fever in Singapore, further drop in typhoid fever incidence would require reduction of travel-related cases through greater awareness of food hygiene and effective vaccination.

An outbreak of food poisoning in which 105 persons from various parts of Singapore were affected was traced to one type of green leafy vegetable (Brassica alboglabra) that had been imported. The clinical symptoms were generally mild and the incubation period short (median 2.5 h). The etiology was confirmed when excessive levels of two organophosphorus pesticides--methamidophos (Tamaron/Monitor; 2.4 ppm-31.7 ppm) and profenofos (Selecron/Curacron; 1.1 ppm-5.4 ppm) were detected in the implicated food, and blood cholinesterase levels of the hospitalized patients were depressed by 26.1%-81.4% based on the lower limit of the reference range. All consignments of the implicated vegetables were immediately sealed and destroyed. Monitoring of imported vegetables for excessive pesticide residues has been enhanced.