Haiti: Absence of dengue hemorrhagic fever despite hyperendemic dengue virus transmission

In 1994-1996, 185 strains of dengue (DEN) virus types 1, 2, and 4 were reco vered from febrile United States and other United Nations military personne l in Haiti. We wondered whether risk factors for dengue hemorrhagic fever ( DHF) existed and, if so, were DHF cases occurring among Haitian children. D engue transmission rates were studied in 210 school children (6-13 years ol d) resident in Carrefour Borough, Port-au-Prince, Haiti. When sera were tes ted for plaque-reduction neutralizing antibodies to DEN 1-4 viruses, nearly 85% had antibodies to two or more DEN serotypes. The annual transmission r ate was estimated at 30%, a rate observed in countries endemic for DHE Hait ian DEN 2 isolates were genotype I, which are repeatedly associated with DH F cases in Southeast Asia and American regions. Despite positive virologic pre-conditions, DHF cases were not recorded by experienced Port-au-Prince p ediatricians. These observations, which are reminiscent of those in Africa, provide further evidence of a dengue resistance gene in black populations.