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Dengue !deN-gE

by Craig R. Pringle, BSc, PhD

Dengue is a mosquito-borne viral infection that causes fever, generalized body aches, and, if severe, external and internal bleeding (called dengue hemorrhagic fever).

Dengue is common in the tropics and subtropics worldwide. It is most common in Southeast Asia but is becoming 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 and 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

In the United States, only about 100 to 200 cases have occurred, brought in by tourists returning from affected areas. However each year, about 50 to 100 million cases and about 20,000 deaths occur worldwide.

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

Symptoms 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 may briefly appear on the face.

Symptoms last for 2 or 3 days, then subside. People usually feel well for about 24 hours. Then, the fever may return, and a rash may appear on the trunk and spread to the limbs and face.

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 results 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

  • 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.

It is usually diagnosed by blood tests for antibodies to the virus.

Prevention

People who live in areas where dengue is common should try to prevent mosquito bites.

People who have dengue are kept under mosquito netting until the second bout of fever resolves to prevent further spread of the infection by mosquitoes.

Vaccines are being tested but are not ready for routine use.

Treatment

  • 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 (see Reye Syndrome).

For dengue hemorrhagic fever, fluids are given intravenously to increase and maintain blood pressure and thus prevent shock.

Drugs Mentioned In This Article

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  • TYLENOL