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 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). 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 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 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.
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. (Antibodies are proteins produced by the immune system to help defend the body against a particular attacker, such as the dengue virus.)
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. This measure helps prevent further spread of the infection by mosquitoes.
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.
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.