257 cases of acute hepatitis B were reported between January 1977 and June 1979. This constituted about one-third of all reported acute viral hepatitis cases in Singapore. The mean annual morbidity and mortality rates per 100,000 was 4.4 and 0.12 respectively. The case-fatality rate was 2.7%. The age-specific morbidity rates were high in the 15-24 and 25-34 years age groups, while the ethnic specific morbidity rate was highest in Indians. The male to female ratio was 4.6: 1. Cases were concentrated in urban and suburban areas with high population density. Three outbreaks, one traced to contaminated needles and syringes, one to contaminated tattoo neeedles, and amongst close contacts, were described. Although parenteral procedures were associated with hepatitis B infection (p < 0.005), non-parenteral or inapparent parenteral mode of transmission probably contributes to a significant extent in the transmission of hepatitis B in Singapore. Studies to determine the role of perinatal transmission, and of vectors, in maintaining the endemicity of the disease, were suggested.
A serological study on dengue infection conducted in Singapore during the period 1982 to 1984 showed that 54.4% of the healthy population between 6 months and over 50 years of age surveyed possessed no haemagglutination-inhibition antibody to dengue type 2 virus. Children below 10 years of age showed the lowest antibody prevalence and were at the greatest risk, with 96.6% susceptible to infection, whereas virtually all adults over 40 showed evidence of prior dengue infection. The geometric mean titre showed a rising trend indicating continuing acquisition of infection in the older age groups. The seropositivity rate of dengue infection of males was twice that of females. Among the 3 major ethnic groups, no significant difference in seropositivity was noted between the Malays and Indians, but the differences between Malays and Chinese and between Indians and Chinese were statistically significant. The study confirmed that the successful implementation of the nation-wide Aedes control programme is reducing endemic dengue virus transmission in the country.
To assess the impact of past dengue epidemics in Singapore, we undertook a national seroepidemiological study to determine the prevalence of past dengue virus (DENV) infection in the adult population in 2010 and make comparisons with the seroprevalence in 2004. The study involved residual sera from 3293 adults aged 18-79 years who participated in a national health survey in 2010. The overall prevalence of anti-DENV IgG antibodies was 56·8% (95% confidence interval 55·1-58·5) in 2010. The seroprevalence increased significantly with age. Males had significantly higher seroprevalence than females (61·5% vs. 53·2%). Among the three major ethnic groups, Malays had the lowest seroprevalence (50·2%) compared to Chinese (57·0%) and Indians (62·0%). The age-standardized seroprevalence in adults was significantly lower in 2010 (54·4%) compared to 2004 (63·1%). Older age, male gender, Indian ethnicity, permanent residency and being home-bound were independent risk factors significantly associated with seropositivity. About 43% of the Singapore adult resident population remain susceptible to DENV infection as a result of the successful implementation of a comprehensive nationwide Aedes surveillance and control programme since the 1970s. Vector suppression and concerted efforts of all stakeholders in the community remain the key strategy in the prevention and control of dengue.
A survey was conducted between 1995 and 1997 to assess the impact of introduction of unleaded petrol and other public health measures on the blood lead level of the population. The geometric mean blood lead level of 269 government employees as determined by graphite furnace atomic absorption spectroscopy, was 66.0 microg/l, much lower than that recorded before introduction of lead-free petrol. Using multiple regression analysis, factors significantly associated with blood lead levels were: exposure to traffic, age (>50 years) and active smoking. Passive smoking, exposure to recent paint work, consumption of alcohol and traditional medicine were found not to be significantly associated with the blood lead level.
A nation-wide outbreak of 260 cases of DF/DHF with 1 death occurred in Singapore from Apr-Sept 1986. The outbreak originated from 3 separate foci of transmission at the western, south-eastern and north-eastern parts of the island and then spread to other dengue receptive urban and suburban areas. The morbidity rate was highest in young male Chinese adults between 15 and 24 years of age. The outbreak was rapidly brought under control through destruction of adult Aedes mosquitoes, surveys and source reduction of larval breeding habitats, health education and to a certain extent law enforcement. The Aedes population was high in the main foci of transmission although the overall house index was only 1.1. Other factors which could have precipitated the outbreak included waning herd immunity of the human population and continuous introduction of dengue virus into the country.
Two outbreaks involving 31 persons with jaundice are described. All had originally been diagnosed as having viral hepatitis. But subsequent investigations showed that all had been exposed to chloroform at work. Toxic jaundice from chemical exposure presents a similar clinical picture to that of viral hepatitis, but fever appears to be uncommon. Doctors who look after workers should be familiar with the type of work and health hazards of their patients. A knowledge of occupational medicine and epidemiology would enable doctors to help in detecting and preventing
occupational disease.
During 10-19 March 1999, 11 workers in 1 of 2 Singaporean abattoirs developed Nipah-virus associated encephalitis or pneumonia, resulting in 1 fatality. A case-control study was conducted to determine occupational risk factors for infection. Case patients were abattoir A workers who had anti-Nipah IgM antibodies; control subjects were randomly selected abattoir A workers who tested negative for anti-Nipah IgM. All 13 case patients versus 26 (63%) of 41 control subjects reported contact with live pigs (P=.01). Swine importation from Malaysian states concurrently experiencing a Nipah virus outbreak was banned on 3 March 1999; on 19 March 1999, importation of Malaysian pigs was banned, and abattoirs were closed. No unusual illnesses among pigs processed during February-March were reported. Contact with live pigs appeared to be the most important risk factor for human Nipah virus infection. Direct contact with live, potentially infected pigs should be minimized to prevent transmission of this potentially fatal zoonosis to humans.