More Information about dengue fever

History:

The first reported epidemics of dengue fever occurred in 1779 to 1780 in Asia, Africa, and North America; the near simultaneous occurrence of outbreaks on three continents indicates that these viruses and their mosquito vector have had a worldwide distribution in the tropics for more than 200 years.

During most of that time, dengue fever was considered a benign, nonfatal disease of visitors to the tropics. Generally, there were long intervals (10 to 40 years) between major epidemics, mainly because the viruses and their mosquito vector could only be transported between population centers by sailing vessels.

A global pandemic of dengue began in Southeast Asia after World War II and has intensified during the last 15 years.

Epidemics caused by multiple serotypes (hyperendemicity) are more frequent, the geographic distribution of dengue viruses and their mosquito vectors has expanded and DHF has emerged in the Pacific region and the Americas. In Southeast Asia, epidemic DHF first appeared in the 1950s, but by 1975 it had become a leading cause of hospitalization and death among children in many countries in that region.

Clinical features:

* Undifferentiated fever: Infants, children and some adults who have been infected with dengue virus for the first time (i.e. primary dengue infection) will develop a simple fever indistinguishable from other viral infections. Maculopapular rashes may accompany the fever or may appear during defervescence.

* Dengue fever: Most common in older children and adults. It is generally an acute biphasic fever with headache, myalgias, arthralgias, rashes and leucopenia. Although DF is commonly benign, it may be an incapacitating disease with severe muscle and joint pain, particularly in adults, and occasionally with unusual hemorrhage. In dengue endemic areas, DF seldom occurs among indigenous people.

* Dengue hemorrhagic fever: Most common in children less than 15 years of age, but it also occurs in adults. Characterized by the acute onset of fever and associated non-specific constitutional signs and symptoms. There is a hemorrhagic diathesis and a tendency to develop fatal shock (DSS). Abnormal hemostasis and plasma leakage are the main patho-physiological changes, with thrombocytopenia and hemoconcentration presenting as constant findings. Although DHF occurs most commonly in children who have experienced secondary dengue infection, it has also been documented in primary infections.

Etiologic agent: Dengue viruses (DEN-1, DEN-2, DEN-3, and DEN-4)

Incidence: Variable, depending on epidemic activity. Globally, there are an estimated 50 to 100 million cases of dengue fever (DF) and several hundred thousand cases of dengue hemorrhagic fever (DHF) per year. Average case fatality rate of DHF is about 5 percent.

Transmission: Mosquito-borne (Aedes aegypti, Ae albopictus, Ae polynesiensis)

Risk groups: Residents of or visitors to tropical urban areas. Increased severe and fatal disease in children under 15 years. No cross-immunity from each serotype. A person can theoretically experience four dengue infections.

Source: Centers for Disease Control and Prevention (CDC)