To evaluate the seasonal trends of viral respiratory tract infections in a tropical environment, a retrospective survey of laboratory virus isolation, serology and immunofluorescence microscopy in two large general hospitals in Singapore between September 1990 and September 1994 was carried out. Respiratory tract viral outbreaks, particularly among infants who required hospitalization, were found to be associated mainly with respiratory syncytial (RSV) infections (72%), influenza (11%) and parainfluenza viruses (11%). Consistent seasonal variations in viral infections were observed only with RSV (March-August) and influenza A virus (peaks in June, December-January). The RSV trends were associated with higher environmental temperature, lower relative humidity and higher maximal day-to-day temperature variation. Although the influenza A outbreaks were not associated with meteorological factors, influenza B isolates were positively associated with rainfall. These data support the existence of seasonal trends of viral respiratory tract infections in the tropics.

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SUMMARYTo determine whether or not occupational exposure to sewage is associated with a higher seroprevalence of hepatitis A virus (HAV) infection, 600 sewage workers in Singapore were tested for total (IgG and IgM) antibody to HAV by enzyme immunoassay. Using logistic regression with stepwise procedure, the adjusted seroprevalence of sewage workers was 2-2 times higher than that of another nonoccupationally exposed population group. Seroprevalence was significantly correlated with age and educational levels, the association being independent of the occupational association. The epidemiological data in the study show that sewage workers have an increased occupational risk of acquiring HAV infection and should be protected by active immunization.

Study objectives -To describe the prevalence of hepatitis B virus (HBV) 41-2%,61-7%, and 33-3%, respectively (p<0-001). The seroprevalences of hepatitis B surface antigen (6-2%, 8-5%, and 4-5%, respectively) were comparable in the three groups. Using stepwise logistic regression analysis, the adjusted seroprevalences of HBV infection in STD and HIV infected patients were respectively 2-4 times (95% confidence interval (CI), 1-7, 3-3) and 3-3 times (95% CI 1-7, 6-3) higher than in controls. HBV infection rates were higher among Chinese (odds ratio (OR), 1-9; 95% CI 1*6, 3-4) than non-Chinese, and among those aged 25-34 years (OR 2-4; 95% CI 1*6, 3-4), 35-44 years (OR 3-9; 95% CI 2-5, 5.9), and 45+ years (OR 6'2; 95% CI 3-8, 10-2) than in those aged 15-24 years. Sex related factors significantly associated with higher infection rates, independent of age and ethnic group, were reactive VDRL test (OR 2-4; 95% CI 1-2, 4-7), participation in anal intercourse (OR 2-3; 95% CI 1*2, 4-3), and having 10 or more lifetime sexual partners (OR 1-5; 95% CI, 1-0, 2-1). Conclusion -The importance of sexual transmission of HBV in an area of intermediate HBV endemicity was confirmed. Patients attending STD clinics should be routinely screened for HBV markers and those found to be seronegative should be strongly advised to be immunised against this virus. Hepatitis B has been recognised as an important sexually transmitted disease.' Extensive epidemiological studies relating to the sexual transmission of hepatitis B virus (HBV) have been conducted in the low HBV endemic countries of North America and western Europe.2'2 Its role in countries of intermediate and high HBV endemicity, however, is not so clear. This is because in endemic countries, up to 80% of the population may already have been infected before reaching a sexually active age.'3 Evidence on sexual transmission is therefore difficult to obtain. In Sudan, a serosurvey among prostitutes failed to show the significance of sexual transmission of HBV.'4 Based on serological studies of household contacts in Taiwan, '5 China,"6 Hong Kong,'7 and the Middle East,'8 it was concluded that sexual transmission of HBV infection by spouses is oflittle significance. However, a recent study on acute hepatitis B cases conducted in Taiwan, a country highly endemic for HBV, convincingly showed the importance of heterosexual transmission.'9Singapore is a city state of intermediate HBV endemicity with an overall hepatitis B surface antigen (HBsAg) carrier rate of 5% and HBV infection rate of about 25% in the general population.20 The role that sexual transmission of HBV plays has not been fully evaluated and is probably underestimated. Serological surveys showed a sharp increase in HBV prevalence in adolescents and young adults. Among family members of acute hepatitis B cases, the prevalence of HBV infection in spouses (73%) was significantly higher than that in siblings, offspring, and other blood relatives,2' and spouses of hepatitis B e antigen (HBeAg) positive women had a h...

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