Dengue viruses in the Caribbean. Twenty years of dengue virus isolates from the Caribbean Epidemiology Centre

The first isolate of a dengue virus in the Americas was obtained in Trinidad and Tobago in 1953, and several dengue virus isolates were obtained in subsequent years. However, the systematic isolation and typing of dengue viruses in support of virus surveillance and outbreak investigations did not start until the creation of the Caribbean Epidemiology Centre (CAREC) in 1975. Since then, over two thousand viral isolates have been obtained and typed from many countries in the English and Dutch-speaking Caribbean. In this communication, virological data from 17 countries between 1977 and 1996 are presented and analyzed together for the first time with available epidemiological data. Types 1, 2 and 4 were isolated over the period, and geographic and temporal patterns in the distribution of the most prevalent strains are presented. The historical surveillance data is critically assessed. A temporal correlation with reported dengue incidence and rainfall data in Trinidad and Tobago is reported. Recent changes in epidemiological patterns are described, including reference to two large later outbreaks. Risk assessment of complicated forms of dengue virus infections in the Caribbean has been attempted, with some success. The importance of ongoing systematic surveillance is discussed

Molecular diagnosis of dengue by reverse transcriptase-polymerase chain reaction

The techniques of reverse transcriptase-polymerase chain reaction (RT-PCR) and subsequent PCR were employed in the analysis of serum samples from a range of patients from the Caribbean Epidemiology Centre (CAREC) member countries. Results were compared with those from viral isolation and immunofluorescence. In the second part of the study, ten serum samples were stored for one week under four sets of conditions: -20 degrees C, 4 degrees C, 25 degrees C, and thawed (20 degrees C) and frozen (-20 degrees C) daily. After one week of each treatment the samples were analysed by RT-PCR and PCR. 90.4of results from PCR agreed with results from viral isolation (VI) and fluorescent antibody (FA) detection. All PCR positive samples originated from sera collected within five days of the date of onset of fever. Frozen, refrigerated and repeat freeze-thawed samples gave consistent positive results by RT-PCR. After storage at 25 degrees C, however, half the dengue-positive samples were negative by RT-PCR. The results indicate the sensitivity and reliability of this rapid technique and its applicability in the Caribbean. It provides a preliminary assessment of its advantages and limitations under certain conditions of serum collection and storage.