An insular outbreak of dengue hemorrhagic fever. I. Epidemiologic observations.

Summary Between 10 July and 23 October 1966 an epidemic of dengue hemorrhagic fever occurred on an island in the Gulf of Thailand. Fourteen cases of dengue-shock syndrome (with one death) and 20 of hemorrhagic-fever syndrome due to dengue occurred. An additional 65 cases of less severe dengue were seen. The 99 patients ranged in age from 1 to 15 years, with a median of 6.7 years; the female-to-male ratio was 55:44. The attack rate for the age group under 15 was 0.75% for the island as a whole, but reached 14% in one village. Dengue virus types 1, 2, or 3 were isolated from a total of 25 patients. Patients were categorized clinically and, independently, by serologic response to dengue. The syndromes of undifferentiated fever, dengue fever, and hemorrhagic fever were not found to be uniformly associated with dengue virus. Shock syndrome as defined was seen only in association with dengue and appeared to be a specific manifestation in the epidemiologic context cited. The median age in cases of mild illness was lower than that for either hemorrhagic fever or shock syndromes. The data presented are consistent with the hypothesis that the dengue-shock syndrome is due to an immunologic phenomenon associated with a second, or subsequent, dengue infection.