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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
CDC. Aedes albopictus infestation--United States, Brazil.
MMWR
1986;35:493-5.
CDC. Aedes albopictus introduction--Texas. MMWR
1986;35:141-2.
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