Epidemiological characteristics of the 2005 and 2007 dengue epidemics in Singapore – similarities and distinctions

INTRODUCTION: We investigated the epidemiological features of the 2007 dengue outbreak to determine the factors that could have triggered it two years after the previous large outbreak in 2005. METHODS: All laboratory-confirmed cases of dengue reported during the year, as well as entomological and virological data, were analysed. RESULTS: A total of 8826 cases including 24 deaths were reported in 2007, giving an incidence of 192.3 cases per 100 000 residents and a case-fatality rate of 0.27%. The median age of the cases was 37 years (interquartile range 25 to 50), with an age range from two days to 101 years, which was higher than the median age of 31 years (interquartile range 20 to 42), with a range from four days to 98 years, in 2005. The overall Aedes premises index in 2007 was 0.68%, lower than the 1.15% observed in 2005. The predominant dengue serotype in 2007 was dengue virus DENV-2 which re-emerged with a clade replacement in early 2007, and overtook the predominant serotype (DENV-1) of 2005. Seroprevalence studies conducted in the three largest outbreak clusters revealed that 73.2% of residents with recent infection were asymptomatic. DISCUSSION: With the exception of an increase in the median age of the cases, and a change in the predominant dengue serotype, the epidemiological features of the 2007 epidemic were largely similar to those of 2005. Singapore remains vulnerable to major outbreaks of dengue, despite sustained vector control measures to maintain a consistently low Aedes premises index.

Clima e epidemias de dengue no Estado do Rio de Janeiro / Climate and dengue epidemics in State of Rio de Janeiro

As temperaturas dos primeiros trimestres do período de 1986-2003, especialmente as mínimas, mostraram-se significativamente mais altas nos anos em que as epidemias de dengue tiveram início na Cidade do Rio de Janeiro. Não houve relação significativa com o total das precipitações pluviométricas para os mesmos trimestres, contudo, as epidemias foram mais freqüentes nos anos em que o volume de chuvas no verão foi pequeno (abaixo de 200mm).

Temperatures in the city of Rio de Janeiro in the first quarter of the year over the period 1986-2003, especially the minimum, were significantly higher in the years in which dengue epidemics started in the city. There was no significant relationship with total rainfall for the same quarter of the year, but epidemics were more frequent in the years in which the volume of rain during the summer was small (less than 200mm).