Dengue

Dengue Fever


Description

Dengue fever and dengue hemorrhagic fever (DHF) are viral diseases transmitted by Aedes mosquitoes, usually Aedes aegypti. The four dengue viruses (DEN-1 through DEN-4) are immunologically related, but do not provide cross-protective immunity against each other.


Occurrence

Dengue, a disease found in most tropical and subtropical areas of the world, hasbecome the most common arboviral disease of humans. More than 2.5 billion persons now live in areas where dengue infections can be locally acquired (1). Reported attack rates for disease during epidemics range from 1 per hundred to 1 per thousand of the population (2). However, because persons with milder illness may not seek medical attention and subsequently be reported, the actual number ofinfections in a population may be 5 to 10 times greater than the number reported. Epidemics caused by all four virus serotypes have become progressively more frequent and larger in the past 25 years. As of 2005, dengue fever is endemic in most tropical countries of the South Pacific, Asia, the Caribbean, the Americas, and Africa (see Maps 4-1, 4-2). Additionally, most tropical urban centers in theseregions have multiple dengue virus serotypes co-circulating (hyperendemicity), which is associated with increased dengue transmission and the appearance of DHF. Future dengue incidence in specific locales cannot be predicted accurately, but a high level of dengue transmission is anticipated in all tropical areas of the world for the indefinite future. The incidence of the severe disease, DHF, hasincreased dramatically in Southeast Asia, the South Pacific, and the American tropics in the past 25 years, with major epidemics occurring in many countries every 3-5 years. The first major epidemic in the Americas occurred in Cuba in 1981, and a second occurred in Venezuela in 1989-1990 (3,4). Since then, outbreaks and rates of endemic, confirmed DHF have occurred in most tropical Americancountries. After an absence of 35 years, several locally acquired cases of dengue fever occurred in southern Texas in 1980 associated with epidemic dengue in adjacent states in Mexico (5). In the last decade, such dengue cases have been identified in Texas every 1 to 5 years. The most recent cases in 2005 included the first locally acquired DHF case in the continental United States (6). After an absence of56 years, a limited outbreak of dengue fever occurred in Hawaii in 2001, associated with imported cases arriving from areas with epidemic dengue in the South Pacific (7).


MAP 4-01 Distribution of dengue, Western Hemisphere.

[pic]

Risk for Travelers

The principal mosquito vector, Ae. aegypti, is most frequently found in or near human habitations and prefers to feed on humans duringthe daytime. It has two peak periods of biting activity: in the morning for several hours after daybreak and in the late afternoon for several hours before dark. Nevertheless, the mosquito may feed at any time during the day, especially indoors, in shady areas, or when it is overcast. Mosquito breeding sites include artificial water containers such as discarded tires, uncovered water storagebarrels, buckets, flower vases or pots, cans, and cisterns.

Cases of dengue fever and DHF are confirmed every year in travelers returning to the United States after visits to tropical and subtropical areas (8). Studies of military and relief workers placed the estimated risk for travelers returning from dengue-endemic areas near one illness per thousand travelers (9, 10). This estimate may overstatethe danger for tourists who may have less contact with the vector when they stay only a few days in air-conditioned hotels with well-kept grounds, or when they participate in outdoor recreational activities where the vector mosquito may be absent (such as sunbathing or playing golf in the middle of the day). A recent study of tourists visiting Hawaii during a dengue outbreak in 2001 failed to...