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Dengue Fever
Description
Dengue fever and dengue hemorrhagic fever (DHF)
are viral diseases transmitted by Aedes mosquitoes, usually Ae.
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 rapidly expanding disease in most tropical
and subtropical areas of the world, has become the most important
arboviral disease of humans. More than 2.5 billion persons now live
in areas at risk of infection, and an estimated 50 million–100
million cases of dengue fever occur each year, 200,000–500,000
of which are DHF. The case-fatality rate for DHF averages 5%. Epidemics
caused by all four virus serotypes have become progressively more
frequent and larger in the past 20 years. As of 2002, dengue fever
is endemic in most tropical countries of the South Pacific, Asia,
the Caribbean, the Americas, and Africa (see Map
3–1). Additionally, most tropical urban
centers in these regions have multiple dengue virus serotypes co-circulating
(hyperendemicity), which increases dengue transmission and the risk
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, has increased dramatically
in Southeast Asia, the South Pacific, and the American tropics in
the past 20 years, with major epidemics occurring in many countries
every 3–5 years. DHF is an emerging disease in the Americas.
The first major epidemic occurred in Cuba in 1981, and a second major
epidemic of DHF occurred in Venezuela in 1989 and 1990. Since then,
outbreaks or sporadic cases, or both, of confirmed DHF have occurred
in 28 tropical American countries. After an absence of 35 years,
a small number of autochthonous cases of dengue fever have been documented
in the continental United States (southern Texas in 1980, 1986, and
1995), associated with imported cases and epidemic dengue in adjacent
states in Mexico. After an absence of 56 years, a limited outbreak
of dengue fever occurred in Hawaii in 2001, associated with imported
cases and epidemic dengue in the South Pacific.
Risk for Travelers
International travelers are at risk for dengue infection,
especially if an epidemic is in progress. Cases of dengue are confirmed
every year in travelers returning to the United States following
visits to tropical and subtropical areas. Travelers to endemic and
epidemic areas, therefore, should be advised to take precautions
to avoid mosquito bites. The principal vector mosquito, Ae. aegypti,
prefers to feed on humans during the daytime and most frequently
is found in or near human habitations. There are two peak periods
of biting activity, in the morning for several hours after daybreak
and in the late afternoon for several hours before dark. The mosquito
may feed at any time during the day, however, especially indoors,
in shady areas, or when it is overcast. Mosquito breeding sites include
artificial water containers such as discarded tires, uncovered barrels,
buckets, flower vases or pots, cans, and cisterns.
Although not completely understood, current data
suggest that, in addition to virus strain, the immune status (i.e.,
having had a previous dengue infection), age, and genetic background
of the human host are the most important risk factors for developing
DHF. In Asia, where herd immunity is high, DHF is observed most commonly
in infants and children <15 years of age who are experiencing
a second dengue infection. In the Americas and the Pacific, where
herd immunity is lower, it is more common to observe DHF in older
children and adults. International travelers from nonendemic areas
(such as the United States) are generally at low risk for DHF infection.
There is little information in published reports about the risk of
dengue infection in pregnant women. In spite of many epidemics, no
increase in congenital malformations has been noted after dengue
epidemics. A small number of recently reported cases suggests that
if the mother is ill with dengue around the time of delivery, the
child can be born with dengue or can acquire dengue through the delivery
process itself.
Clinical Presentation
Dengue fever is characterized by sudden onset after
an incubation period of 3–14 days (most commonly 4–7
days), high fever, severe frontal headache, and joint and muscle
pain. Many patients have nausea, vomiting, and rash. The rash appears
3–5 days after onset of fever and can spread from the torso
to the arms, legs, and face. The disease is usually self-limited,
although convalescence can be prolonged. Many cases of nonspecific
viral syndrome or even subclinical infection occur, but dengue can
also present as a severe, sometimes fatal hemorrhagic disease called
DHF.
Dengue should be considered by physicians in the
differential diagnosis of all patients who have fever and a history
of travel to a tropical area within 3 weeks of onset of symptoms.
For diagnosis, acute- and convalescent-phase serum samples should
be obtained and sent through state or territorial health department
laboratories to CDC's Dengue Branch, Division of Vector-Borne Infectious
Diseases, National Center for Infectious Diseases, 1324 Calle Cañada,
San Juan, Puerto Rico 00920–3860. Serum samples should be accompanied
by clinical and epidemiologic information, including the date of
disease onset, the date of collection of the sample, and a detailed
recent travel history. For additional information, the Dengue Branch
can be contacted at: telephone 1-787-706-2399; fax 1-787-706-2496;
e-mail hseda@cdc.gov; or the DVBID website at http://www.cdc.gov/ncidod/dvbid/dengue/index.htm.
Prevention
No vaccine is available. Travelers should be advised
that they can reduce their risk of acquiring dengue by remaining
in well-screened or air-conditioned areas when possible, wearing
clothing that adequately covers the arms and legs, and applying insect
repellent to both skin and clothing. The most effective repellents
are those containing N,N-diethylmetatoluamide (DEET). (See
Protection against Mosquitoes and Other Arthropods.)
Treatment
Acetaminophen products are recommended for managing
fever. Acetylsalicyclic acid (aspirin) and nonsteroidal antiinflammatory
agents (such as ibuprofen) should be avoided because of their anticoagulant
properties. Patients should be encouraged to rest and take abundant
fluids. In severe cases, the prompt infusion of intravenous fluids
is necessary to maintain adequate blood pressure. Because shock may
develop suddenly, vital signs must be monitored frequently. Hypotension
is a more frequent complication of DHF than severe hemorrhage.
— Gary
Clark, Duane Gubler, Jose Rigau
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