Epidemiology of dengue fever in Trinidad, West Indies: the outbreak of 1998

The first outbreaks of dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) in the Americas followed the introduction of two new dengue serotypes (DEN 1 and DEN 2) into the region in 1977 and 1981 respectively (Gubler and Kuno 1997). The discontinuation of several programmes to control Aedes aegypti in the region in the 1970s and early 1980s also added to the burden of disease attributable to the dengue virus (Kouri et al. 1989; Rico- Hesse 1990). Today DHF and DSS are on the increase throughout the Caribbean region where 700000 cases of classical dengue and 6000 cases of DHF were recorded in 1998 and 1995 respectively (Gubler and Kuno 1997; Pinheiro and Corber 1997; Keating 2001). In Trinidad the continuation of programmes to control Ae. aegypti throughout the 1980s and 1990s resulted in a slower increase in the incidence of classical dengue than observed elsewhere in the Caribbean but a significant increase from 17 cases in 1981 to >2000 in 1997 was still recorded (Keating 2001). DHF was relatively late in reaching Trinidad the first few cases (five) not being seen until 1992 (Teelucksingh et al. 1997) but is also gradually becoming more common - there were 108 cases in 1997 (Chadee 2001). The increases in the incidence of classical dengue and DHF in Trinidad have been caused by numerous factors including the importation of new dengue serotypes (Rico-Hesse 1990) larger vector populations (Chadee 2001) behavioural changes in the vector (Chadee and Martinez 2000) demographic changes (Gubler and Kuno 1997; Chadee and Martinez 2000) and the immunological naivity of most of the human population (Focks and Chadee 1997). It also seems likely that the percentage of cases of dengue who are detected and recorded has increased over the last two decades with under-reporting being more of a problem before the arrival of DHF and the occurrence of severe illness and deaths attributable to the dengue virus. The recent importation of DEN 3 from South-east Asia has increased the risk of DHF outbreaks in the entire Caribbean region including Trinidad (Chadee and Martinez 2000). In the present study the spatial and temporal distributions of classical dengue and DHF in Trinidad in 1998 were investigated so that the epidemiology of these illnesses could be better understood. (excerpt)