Dengue Fever
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Dengue (pronounced den' gee) is a disease caused by any one of four closely related
viruses (DEN-1, DEN-2, DEN-3, or DEN-4). The viruses are transmitted to humans
by the bite of an infected mosquito. In the Western Hemisphere, the
Aedes
aegypti mosquito is the most important transmitter or vector of dengue
viruses, although a 2001 outbreak in Hawaii was transmitted by
Aedes albopictus.
It is estimated that there are over 100 million cases of dengue worldwide each
year.
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DHF is a more severe form of dengue. It can be fatal if unrecognized and not properly
treated. DHF is caused by infection with the same viruses that cause dengue. With
good medical management, mortality due to DHF can be less than 1%.
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Dengue is transmitted to people by the bite of an
Aedes mosquito
that is infected with a dengue virus. The mosquito becomes infected with dengue
virus when it bites a person who has dengue or DHF and after about a week can
transmit the virus while biting a healthy person. Dengue cannot be spread directly
from person to person.
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The principal symptoms of dengue are high fever, severe headache, backache, joint
pains, nausea and vomiting, eye pain, and rash. Generally, younger children have
a milder illness than older children and adults.
Dengue hemorrhagic
fever is characterized by a fever that lasts from 2 to 7 days, with
general signs and symptoms that could occur with many other illnesses
(e.g., nausea, vomiting, abdominal pain, and headache). This stage is
followed by hemorrhagic manifestations, tendency to bruise easily or other
types of skin hemorrhages, bleeding nose or gums, and possibly internal
bleeding. The smallest blood vessels (capillaries) become excessively
permeable (“leaky”), allowing the fluid component to escape from the blood
vessels. This may lead to failure of the circulatory system and shock,
followed by death, if circulatory failure is not corrected.
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There is no specific medication for treatment of a dengue infection. Persons who
think they have dengue should use analgesics (pain relievers) with acetaminophen
and avoid those containing aspirin. They should also rest, drink plenty of fluids,
and consult a physician.
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As with dengue, there is no specific medication for DHF. It can however be effectively
treated by fluid replacement therapy if an early clinical diagnosis is made. Hospitalization
is frequently required in order to adequately manage DHF. Physicians who suspect
that a patient has DHF may want to consult the Dengue Branch at CDC, for more
information.
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Outbreaks of dengue occur primarily in areas where
Aedes aegypti (sometimes
also
Aedes albopictus) mosquitoes live. This includes most tropical
urban areas of the world. Dengue viruses may be introduced into areas by travelers
who become infected while visiting other areas of the tropics where dengue commonly
exists.
In the America
region, all dengue virus serotypes are now present. DEN-3 was reintroduced
into Central America in 1994 and is now found in several countries in the
region. Since this serotype has been absent from the Americas for almost
20 years, the population has a low level of immunity and the virus is
expected to spread rapidly.
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There is no vaccine for preventing dengue. The best preventive measure for residents
living in areas infested with
Aedes aegypti is to eliminate the
places where the mosquito lays her eggs, primarily artificial containers that
hold water.
Items that collect
rainwater or are used to store water (for example, plastic containers,
55-gallon drums, buckets, or used automobile tires) should be covered or
properly discarded. Pet and animal watering containers and vases with
fresh flowers should be emptied and scoured at least once a week. This
will eliminate the mosquito eggs and larvae and reduce the number of
mosquitoes present in these areas.
For travelers to
areas with dengue, a well as people living in areas with dengue, the risk
of being bitten by mosquitoes indoors is reduced by utilization of air
conditioning or windows and doors that are screened. Proper application of
mosquito repellents containing 20% to 30% DEET as the active ingredient on
exposed skin and clothing decreases the risk of being bitten by
mosquitoes. The risk of dengue infection for international travelers
appears to be small, unless an epidemic is in progress.
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The emphasis for dengue prevention is on sustainable, community-based, integrated
mosquito control, with limited reliance on insecticides (chemical larvicides and
adulticides). Preventing epidemic disease requires a coordinated community effort
to increase awareness about dengue/DHF, how to recognize it, and how to control
the mosquito that transmits it. Residents are responsible for keeping their yards
and patios free of sites where mosquitoes can be produced.
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