• Vol. 38 No. 8, 667–675
  • 15 August 2009

Seroepidemiology of Dengue Virus Infection Among Adults in Singapore

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ABSTRACT

Introduction: To determine the seroepidemiology of dengue virus infection in a representative sample of the adult resident population aged 18 years old to 74 years old in Singapore and to estimate the proportion of asymptomatic dengue infection during the 2004 epidemic. Materials and Methods: The study was based on 4152 stored blood samples collected between September and December 2004 from participants aged 18 years old to 74 years old during the 2004 National Health Survey. Sera were tested for IgG and IgM antibodies using a commercial test kit (PanBio Capture/Indirect ELISA). Results: Of the study population, 59.0% and 2.6% tested positive for dengue IgG (past infection) and IgM/high-titre IgG (recent infection), respectively. Only 17.2% of young adults aged 18 years old to 24 years old were dengue IgG positive. Multivariate analyses showed that older age, Indian ethnicity and male gender were significantly associated with past infection, whereas only age was significantly associated with recent dengue infection. Based on the dengue cases notified during the period of survey, it was estimated that for every 23 individuals recently infected with dengue, only 1 was reported to the health authority as a clinical case. Conclusion: The Singapore population is highly susceptible to dengue epidemics despite its aggressive Aedes prevention and control programme. The finding of a high proportion of unreported cases due to asymptomatic and subclinical infection poses a challenge for dengue control.


Dengue fever is a mosquito-borne viral disease endemic in Singapore as well as in the surrounding Southeast Asian countries.1 It is a re-emerging disease of concern.2 Although Singapore has a well-established nationwide Aedes mosquito control programme that includes source reduction, public health education and law enforcement since the 1970s, there has been an increasing trend in the number of notifi ed dengue cases in the past 15 years with 6-year cyclical epidemics occurring in 1992, 1998 and 2004.3 The Aedes premises index (percentage of premises positive for Aedes breeding) has been maintained at 1% to 2% since the 1980s. In 2005, Singapore witnessed the largest ever recorded epidemic with a total of 14,209 dengue cases. The epidemiology of dengue has changed. It is no longer a childhood infection, but involved mainly young adults aged between 25 and 34 years of age.4 To assess the impact of the cyclical epidemics on the prevalence of dengue virus infection in the general population, a seroepidemiological study was conducted in 2005.

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