Dengue activity in Puerto Rico, 1990.

Reported dengue activity in Puerto Rico (PR) increased in 1990 for the fourth consecutive year. The Community Hygiene Division of the PR Health Department received 9,540 reports of suspected dengue cases. Of the blood samples obtained from 7,660 patients, 1,911 were confirmed as dengue infection by laboratory tests at the Dengue Branch, San Juan Laboratories, Centers for Disease Control. Dengue 2 (DEN-2) continued to be the most frequently isolated serotype among all confirmed cases, hospitalized patients, and the confirmed cases with hemorrhagic manifestations. Disease was reported throughout the island and during all months, but activity, as in previous years, was lowest from April through July, and highest from September to November. The highest rates of laboratory-confirmed illness occurred in towns on the south coast and in the central mountains, with only one or two circulating virus serotypes (DEN-2 in the south; DEN-2 and DEN-4 in the central mountains). Although cases were confirmed in infants and octogenarians, the majority of laboratory-confirmed cases (1,293, 68%), and the highest attack rates (0.70/1000), were reported in persons younger than 30. Of patients with confirmed cases, 289 (15%) were hospitalized, and 438 (23%) reported at least one hemorrhagic manifestation. One presumptive dengue case with fatal outcome was reported in 1990 in a 17-year-old woman in whom a febrile illness, seizures, and coma developed; she died after cardiorespiratory arrest. Recent dengue infection in this individual was serologically documented, but no virus was isolated.