Dengue in the Americas, 1985

The Americas experienced increased dengue activity in 1985 with 68,998 cases reported as compared to 43,435 cases in 1984 and 25,216 cases in 1983. In 1985, as in 1983 and 1984, three serotypes (DEN-1, DEN-2, and DEN-4) circulated in the region. Twenty countries reported dengue activity, and the serotype was confirmed by virus isolation and/or serology in 14. Although all three serotypes were widely distributed in 1985, DEN-1 continued to be the predominant virus serotype in the region. Three countries (Mexico, Puerto Rico, and Venezuela) had three serotypes circulating simultaneously (DEN-1, DEN-2, and DEN-4), while five other countries had at least two serotypes (Table 1).

Nicaragua and Aruba experienced major dengue epidemics in 1985. Small numbers of cases with severe and fatal hemorrhagic disease were reported in both countries. The Nicaraguan Ministry of Health reported 17,483 cases of dengue, most of which occurred late in the year. DEN-1 was the predominant virus isolated (18 strains), but DEN-2 was also isolated (8 strains). In addition, seven cases of fatal hemorrhagic disease in adults were reported, and one was confirmed as DEN-1 by virus isolation. Aruba, Netherland Antilles, reported 24,000 cases of dengue during a DEN-1 epidemic that began in late 1984 and continued through March 1985. There was one virologically confirmed case of fatal hemorrhagic disease (DEN-1) in an adult female. A sibling of this patient died of a similar hemorrhagic disease 3 weeks earlier; however, the disease was not confirmed as dengue.

Dengue transmission continued in Mexico, but to a lesser extent than in the previous 2 years. Honduras and El Salvador also reported dengue activity. In South America, both Colombia and Venezuela had confirmed dengue transmission. While three serotypes were confirmed in Venezuela, no outbreaks were reported. Beginning in October, the southern port city of Tumaco, Colombia, experienced a mixed outbreak of DEN-1 and DEN-2. A total of 7,797 cases were reported in the whole country in 1985. DEN-2 was the predominant serotype isolated in Colombia in 1985.

With the exception of a small outbreak in Puerto Rico, dengue activity in the Antilles islands remained sporadic in 1985. In Puerto Rico, 133 cases were confirmed from late August through December. Two cases of hemorrhagic disease in children were confirmed by virus isolation--one DEN-1 with a primary-type serologic response and one DEN-2 with a secondary-type response. Forty-eight cases of suspected dengue were reported in the United States. However, only eight cases were confirmed, and all of these had been imported.

Clinically, most of the illness reported in the Americas in 1985 was of the classical type. However, there appears to be increased sporadic incidence of hemorrhagic disease associated with dengue infection in most countries of the region. Reported by Pan American Health Organization, Washington, DC; Caribbean Epidemiology Center, Port-of-Spain, Trinidad; Pasteur Institute, Cayenne, French Guiana; Instituto de Salubridad y Enfermedades Tropicales, Mexico City, Mexico; Instituto Nacional de Salud, Bogota, Colombia; Instituto Nacional de Higiene "Rafael Rangel," Caracas, Venezuela; Institute of Tropical Medicine "Pedro Kouri," Havana, Cuba; Puerto Rico Health Dept, San Juan, Puerto Rico; Dengue Br, Div of Vector-Borne Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: For the past several years, dengue transmission in the Americas has been characterized by more frequent epidemic activity. More countries have been reporting severe hemorrhagic disease, and the total number of cases of severe hemorrhagic disease has increased. The number of circulating dengue virus serotypes has also increased. In Asia, dengue fever changed from a benign flu-like illness to become one of the leading causes of morbidity and mortality among southeast Asian children. The current epidemiologic pattern of dengue in the Americas is similar to the pattern that occurred in southeast Asia in the 1950s.

It is often believed that the highest risk for dengue hemorrhagic fever (DHF) is associated with DEN-2 infection. This serotype, while widespread in the region, has only occurred sporadically in recent years. Although secondary infection with DEN-2 is a definite risk factor for DHF, most severe and fatal cases of DHF in 1984 and 1985 were caused by DEN-1 or DEN-4. Furthermore, DEN-3 has been shown to cause severe and fatal DHF in some countries of southeast Asia. Thus, health authorities should assume that all four serotypes are capable of causing epidemics of DHF, and they should act to establish proper surveillance for the disease.

Aedes albopictus (1,2), an efficient Asian mosquito host for dengue viruses, has recently been discovered in the United States and Brazil. This aggressive, man-biting mosquito has both rural and urban habitats. It also has been shown to transmit dengue viruses both transovarially (from female mosquitoes to their offspring through infection of the eggs) and from man to man. If Ae. albopictus becomes involved in dengue transmission in the Americas, then the situation in this region would become even more similar to the situation in southeast Asia. The presence of Ae. albopictus in the Americas adds further stimulus for surveillance of dengue and DHF in the region.

References

1. CDC. Aedes albopictus infestation--United States, Brazil. MMWR 1986;35:493-5.

2. CDC. Aedes albopictus introduction--Texas. MMWR 1986;35:141-2.

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