• Vol. 40 No. 10, 439–447
  • 15 October 2011

Changing Epidemiological Patterns of Hepatitis A Infection in Singapore

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ABSTRACT

Introduction: Singapore has experienced remarkable socioeconomic progress over the last few decades, with a corresponding rise in standards of sanitation and living conditions. We undertook a study to describe its epidemiological trends of hepatitis A over the last 2 decades.

Materials and Methods: We analysed the epidemiological data on all laboratory-confirmed cases of hepatitis A from 1990 to 2009. We also described 3 outbreaks which occurred in 1991, 1992 and 2002. To determine the changing prevalence of hepatitis A virus (HAV) infection, we compared the findings from a seroepidemiological study conducted in 1993 with earlier surveys in 1975 and 1984/1985.

Results: The incidence of indigenous hepatitis A cases per 100,000 population declined significantly from 1.8 in 1989 to 0.7 in 2009, and more than half were imported. While majority of the imported cases were Singapore residents, the proportion of imported cases among Singapore residents had decreased significantly. Most of the Singapore residents contracted the disease from Southeast Asia and the Indian subcontinent. The overall prevalence of HAV infection in the population declined from 31.8% in 1984/85 to 25.9% in 1993.

Conclusion: The incidence and seroprevalence of hepatitis A in Singapore are comparable to other developed countries. As Singapore is situated in a region highly endemic for HAV, it is very vulnerable to the introduction of the disease because of the high volume of regional travel and import of food, especially shellfish. While we note that there have been no further shellfish-associated outbreaks since 2002, sustained vigilance, strict control of food import by the authorities and public health education on the risk of consuming shellfish, especially cockles, raw and half-cooked, should be maintained.


Hepatitis A virus (HAV) is a ribonucleic acid (RNA) picornavirus transmitted by the faecal-oral route, either from person to person or through contaminated food or water. The clinical manifestations vary with age, and its severity and fatality increase with age. HAV is usually silent or subclinical in children, and on a worldwide scale fewer than 5% of infections are recognised clinically. Asymptomatic infection is much more common in children less than 6 years of age compared with older children and adults. The mean incubation period is approximately 30 days, with a range of 2 to 6 weeks. The infection usually results in an acute self-limited illness and only rarely leads to fulminant hepatic failure. Approximately 85% of individuals infected with HAV have full recovery within 3 months, and nearly all have complete recovery by 6 months.

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