ABSTRACT
In 1986 Puerto Rico experienced its eleventh dengue outbreak of this century, but the first with simultaneous transmission of three dengue virus serotypes, and the first with significant numbers of severe and fatal hemorrhagic disease. Overall, 10,659 cases were reported; 1,257 cases were laboratory confirmed as having current or recent dengue infection. Dengue 4 (DEN-4) was the predominant serotype (160/363 isolates, 44 percent) followed by dengue 1 (DEN-1) with 134 isolates (37 percent) and dengue 2 (DEN-2), 69 isolates (19 percent). Transmission peaked during September, but large numbers of cases occurred through November. Seventy-one (91 percent) of Puerto Rico's 78 municipalities had laboratory-confirmed cases. Fifty-one percent of all confirmed cases occurred in metropolitan San Juan. Most cases presented clinically as classical dengue fever, but 37 percent of all confirmed cases were reported to have developed some type of hemorrhagic manifestation, and 6 percent reported hematemesis. In addition, 29 laboratory confirmed cases met the WHO case definition for dengue hemorrhagic fever, 3 of which were fatal. Among the 29 laboratory-confirmed cases of dengue hemorrhagic fever/ dengue shook syndrome, virus was isolated from 12; one DEN-1, three DEN-2, and eight DEN-4. Among laboratory confirmed cases, infants less than one year of age were at greater risk of developing dengue hemorrhagic fever/ dengue shook syndrome, hematemesis and any reported hemorrhage than were the other age groups evaluated