Dengue fever is caused by one of four strains of dengue virus and is transmitted to humans most commonly by the Aedes aegypti mosquito during a blood meal.
The global distribution of dengue is similar to that of malaria. In 2005, the World Health Organization estimated that 2.5 billion people live in areas at risk for epidemic transmission. The dengue virus is endemic in tropical Asia, eastern and western Africa, Polynesia, Micronesia, the Caribbean, Central America, South America and Australia (Dengue distribution map). Although the Aedes aegypti mosquito is the main vector, two other Aedes species may also act as vectors for dengue virus transmission – Aedes albopictus (southeast Asia) and Aedes niveus (Malaysia).
There are four serotypes of dengue and all four strains are endemic in many areas (DEN-1, DEN-2, DEN-3 and DEN-4). Epidemics caused by multiple serotypes are common. Although infection provides lifelong immunity against the infecting serotype, it does not confer protection against the other serotypes. Therefore, people who live in dengue-endemic areas can become infected with dengue more than once.
Dengue infections may present as a mild nonspecific viral syndrome (DF), or cause severe hemorrhagic disease (DHF) that may be fatal. Risk factors for severity of infection include the strain of infecting virus, age of the patient, and previous dengue infection history.
Dengue fever (DF):
- Tens of millions of cases occur each year in endemic areas.
- Incubation period of 3-14 days (average 4-7 days).
- Symptoms include sudden onset of high fevers, severe frontal headache, backache, joint and muscle pain, nausea, vomiting, eye pain and rash.
- Disease usually self-limited.
- Illness is usually milder in younger children than older children and adults.
Dengue hemorrhagic fever (DHF):
- Severe form of dengue.
- Hundreds of thousands of cases occur each year.
- Symptoms of acute stage of infection include fever lasting from 2-7 days, nausea, vomiting, abdominal pain, headache.
- Second stage of infection includes hemorrhaging (bruising and skin hemorrhages, bleeding nose or gums, possibly internal bleeding) resulting from fluid leakage from capillaries.
- May lead to shock, and possibly death.
- Mortality rate in most countries approximately 5% (mostly children and young adults).
- Most often occurs in second infections with dengue virus (especially DEN-2 and DEN-3).
Treatment for dengue fever and dengue hemorrhagic fever is supportive: over-the-counter medications for fever, fluids to prevent and treat dehydration, and other supportive measures as necessary. Hospitalization is recommended for dengue hemorrhagic fever to ensure adequate supportive measures. Adequate treatment can reduce the risk of death from dengue hemorrhagic fever to 1%.
Sources:
Dengue Fever (Centers for Disease Control and Prevention)
Dengue Fever (World Health Organziation)
