Dengue
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Dengue is a mosquito-borne viral infection that causes
fever, generalized body aches, and, if severe, external and internal bleeding
(called dengue hemorrhagic fever).
About 50 to 100 million cases of dengue and about 20,000
deaths occur worldwide.
Symptoms vary in severity but may include fever, chills, a
severe headache, pain when the eyes are moved, extreme fatigue, and severe
generalized body aches.
A more severe form, called dengue hemorrhagic fever, may
cause bleeding from the nose, mouth, gastrointestinal tract, and puncture
wounds.
To diagnose dengue, doctors do blood tests to check for the
virus or antibodies to the virus.
A vaccine is available in Mexico, Brazil, Thailand, and some
other countries (not in the United States), but use is restricted to people who
have previously had dengue.
Treatment of dengue focuses on relieving symptoms and, for
dengue hemorrhagic fever, fluids and blood products given intravenously.
Dengue is common in the tropics and subtropics worldwide. It
is most common in Southeast Asia but has become more common in Central and
South America and other countries. It has occurred in the Caribbean (including
Puerto Rico and the U.S. Virgin Islands), in Oceania, and in the Indian
subcontinent. The infection is caused by a flavivirus that is spread by
mosquitoes.
Many factors have contributed to the spread of dengue:
Climate change, resulting in more areas where the mosquito
can live
Spread of the mosquito that carries the virus
Lack of an effective vaccine
Each year, about 50 to 100 million cases and about 20,000
deaths occur worldwide. However, in the United States, only about 100 to 200
cases occur yearly, nearly all brought in by travelers returning from affected
areas. If these travelers live in an area of the United States with Aedes
mosquitoes, the mosquitoes may bite them, then bite other people living in the
area. The dengue virus is thus spread to other people (called local
transmission). Individual infected mosquitoes may bite more than one person,
putting multiple people at risk of infection. A few cases of locally
transmitted dengue have occurred in Hawaii, Florida, and Texas.
There are four types of dengue virus (serotypes). Infection
with one of the serotypes protects against infection with that serotype for a
long time but provides only limited and temporary protection against infection
with the other serotypes.
Symptoms of Dengue
Symptoms of dengue typically begin about 3 to 15 days after
being bitten by an infected mosquito.
Dengue varies in severity. Dengue usually begins suddenly,
causing a fever, chills, a severe headache, pain when the eyes are moved,
extreme fatigue, and severe generalized body aches, particularly in the back,
legs, and joints. These aches are often so painful that the disease has been
called breakbone fever.
Lymph nodes are swollen, and a rash that makes the face look
flushed and red may appear briefly.
Symptoms last for 2 or 3 days, then subside. People usually
feel well for about 24 hours. Then, the fever may return, and a blotchy red
rash may appear first on the back of the hands and top of the feet, then spread
to the arms, legs, and torso.
People with more severe disease may feel weak for several
weeks. Death is rare.
Dengue hemorrhagic fever
Dengue hemorrhagic fever is a more severe form of dengue.
This disorder occurs mainly in children who are under 10 years old and who live
in areas where dengue is common. Dengue hemorrhagic fever can result from a
second infection with a dengue virus. The person's immune system reacts
aggressively to the second infection. This reaction damages blood vessels,
which then leak fluid and/or blood. Sometimes blood vessels leak fluid into the
lungs, causing difficulty breathing.
Bleeding from the nose, mouth, gastrointestinal tract, and
puncture wounds may occur. People may vomit blood or have blood in their stool.
Bleeding may occur under the skin as purplish spots or patches.
Without treatment, illness can worsen rapidly, and blood
pressure may become very low, resulting in shock. When treated by experienced
doctors, dengue hemorrhagic fever is fatal in less than 1% of people. However,
without such care, as many as 30% of people die.
Diagnosis of Dengue
Blood tests
Doctors suspect dengue fever when typical symptoms occur in
people who live or have traveled in an area where the infection is common.
LAB TEST
Dengue Fever Testing icon
It is usually diagnosed by blood tests for antibodies to the
virus. (Antibodies are proteins produced by the immune system to help defend
the body against a particular attacker, such as the dengue virus.)
Prevention of Dengue
People who live in areas where dengue is common should try
to prevent mosquito bites.
To prevent mosquito bites, people should take the following
precautions:
Wear long-sleeved shirts and long pants.
Stay in places that have air conditioning or that use window
and door screens to keep mosquitoes out.
Sleep under a mosquito net in places that are not adequately
screened or air-conditioned.
Use strong insect repellents—those with ingredients such as
DEET (diethyltoluamide) or other approved active ingredients—on exposed skin
surfaces.
Treat clothing and gear with permethrin insecticide (do not
apply it directly to the skin).
People who have dengue are kept under mosquito netting until
the second bout of fever resolves. This measure helps prevent further spread of
the infection by mosquitoes.
For children, the following precautions are recommended:
Do not use insect repellent on infants under 2 months old.
Do not use products containing oil of lemon eucalyptus
(para-menthane-diol) on children under 3 years old.
For older children, adults should spray repellent on their
own hands and then apply it to the children's skin.
Dress children in clothing that covers their arms and legs,
or cover the crib, stroller, or baby carrier with mosquito netting.
Do not apply insect repellent to the hands, eyes, mouth, or
cut or irritated skin of children.
Dengue vaccine
A dengue vaccine is available in Mexico, Brazil, Thailand,
and some other countries, but not in the United States.
Vaccinating people who previously had a mild case of dengue
reduces their risk of developing the severe form of the disease (dengue
hemorrhagic fever) if they are infected again. However, vaccinating people who
never had dengue appears to increase their risk of more severe disease if they
are infected with dengue later. Thus, doctors prefer to use the vaccine only in
people who have previously had dengue. However, in many countries where dengue
is common, it is not always possible for doctors to do a dengue blood test
before they give the vaccine.
Several other dengue vaccines are under study.
Treatment of Dengue
Pain relievers
For dengue hemorrhagic fever, fluids
There are no effective antiviral drugs for dengue. Treatment
focuses on relieving symptoms. Acetaminophen can be used to lower the fever and
relieve muscle aches. But aspirin and other nonsteroidal anti-inflammatory
drugs (NSAIDs) should not be used because they may make bleeding more likely.
Also, aspirin is not given to children because it increases the risk of Reye
syndrome.
For dengue hemorrhagic fever, people are given fluids
intravenously to increase and maintain blood pressure and thus prevent shock.
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