Dengue fever is caused by a flavivirus, which is a class of viruses transmitted to people primarily through the bite of an infected tick or mosquito. For dengue fever, the carrier insect is the female Aedes aegypti mosquito. This mosquito is active during the daytime and most active during the two hours after sunrise and a few hours before sunset. There are four serotypes of dengue virus fever, known as DENV-1, DENV-2, DENV-3 and DENV-4. Infection with one type could result in a nonlethal infection that will give the person immunity to that serotype but not the others. Any single person can catch dengue fever up to four times, once for each serotype. There are three associated diseases with varying levels of severity: dengue fever, dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS).
Dengue Fever Symptoms
Dengue fever is characterized by a sudden onset of fever for up to a week. Other symptoms may include a severe headache, muscle and joint pain, nausea and vomiting. Older children may experience severe back pain. A rash may appear about the same time that the fever subsides. The rash may not be visible in darker-skinned people. There may also be minor bleeding, including bleeding of the gums. Localized outbreaks of dengue fever are frequent, but fatalities are few with proper medical care. There is no vaccine for dengue fever. Medical treatment is to ease the symptoms until the worst of the infection passes.
Dengue Hemorrhagic Fever Symptoms
Dengue hemorrhagic fever (DHF) is a much more severe manifestation of dengue fever. This complication of dengue fever is endemic in southeastern Asia, Africa and Latin America. Symptoms include high fever of up to 105.8°F (41°C) and a tendency for spontaneous abnormal bleeding and blood clotting. Fevers in this very high range can lead to convulsions. Gastrointestinal hemorrhage and liver damage are also signs that dengue fever has become DHF. Treatment includes replacement of fluids lost and transfusion if bleeding is sever. If untreated, dengue hemorrhagic fever is often fatal in children.
Dengue Shock Syndrome Symptoms
Dengue shock syndrome (DSS) occurs after dengue fever has progressed to dengue hemorrhagic fever (DHF) and fluid replenishment and bleeding control have not been established. Because it starts as dengue fever, DSS is preceded by the typical very or very high fever lasting up to a week, hemorrhagic bleeding that is characteristic of DHF, a decrease in circulating platelet counts and evidence of plasma leakage. Dengue shock syndrome causes a rapid, weak pulse, a very narrow blood pressure, restlessness and a cold, clammy skin, plus signs of shock. When shock sets in, the fatality rate can be as high as 50 percent. With appropriate fluid replacement therapy and bleeding controls in place, mortality decreases. Two-thirds of all DSS fatalities are children.
References
- World Health Organization: Dengue Fever
- "Control of Communicable Diseases Manual," 19th ed.; David L. Heymann (ed.), 2008
