Epidemiology of syphilis in Singapore over three decades (1955-1986)

The overall incidence of syphilis in the last three decades has decreased from 93.3 cases per 100,000 population in 1955 to 42.5 in 1986 amidst fluctuations in between. The decrease from 1955 to 1965 might be related to the widespread use of penicillins. The increase from 1965 to 1973 could be attributed to the influx of tourists and the use of Singapore as a rest and recreation centre during the Vietnam war period; better reporting system; and waning herd immunity as a result of disappearance of yaws. The introduction of the Medical Scheme and better contact tracing methods might account for the drop from 1974 to 1979. In the last 7 years, there was some fluctuations in the overall incidence, but the incidence of early infectious syphilis rose from 10 per 100,000 in 1979 to 29 in 1986 with the greatest increase in the female patients with early latent syphilis. Female prostitutes contributed a substantial proportion of all the cases of early infectious cases, accounting for 32% of all the cases in 1984. Moreover, female prostitutes were cited as the main source of contact, 46% in a local study. The incidence rate of congenital syphilis remained low over the last three decades, averaging 0.36 per 1000 live births. Both early and late syphilis occurred most commonly in the 20-29-year-old age group. The male to female ratio changed from 3.5 in 1976 to one in 1986 for early infectious syphilis while the ratio for late syphilis was 0.7 in 1976 and 1 in 1986. The closing of the gap reflects better clinic acceptance by both sexes, good contact tracing and better public health education.