Dengue Fever

Dengue fever and dengue hemorrhagic fever (DHF), caused by the dengue virus, is among the spectrum of acute febrile tropical disease and is transmitted by mosquitoes. Occurring mainly in the tropics it can be life threatening and is caused by four closely related virus stereotypes of the genus Flavivirus. It was identified and named in 1779. It has a nickname of “breakbone fever” due to it causing sever generalized bodyache. It tends to be more prevalent in the urban districts of its range than in rural areas.

There is no long term cross protection since each serotype is sufficiently different. Epidemics tend to be related to a single serotype usually one that is new to a region. The disease is transmitted to humans by Aedes aegypti, mosquitoes. There are 50 million estimated cases of dengue infection each year worldwide. It is an endemic in more than 100 countries.

Symptoms include a sudden onset of fever associated with headache, muscle and joint pain, and rash. The rash is usually a maculopapular rash although later in the illness a hemorrhagic rash of bright red pinpoint spots. The rash usually occurs first on lower limbs and the chest and spreads to cover the rest of the body. Some cases are mild compared to that and are often misdiagnosed as influenza. Travelers from tropical locations often transmit Dengue to areas previously free of the disease. It is only transmitted when someone is carrying a virus in the blood.

Fever usually persists for about two to seven days. Recovery is usually accompanied by fatigue and depression. Platelet count usually drops until a patient’s temperature is normal. These platelets usually reach their lowest point around the fifth or sixth day. Many of those inflicted assume that once the fever passes they are cured, however, platelets are usually still dropping at this point requiring hydration until they begin to rise again.

Some cases result in hemorrhagic phenomena that include bleeding from the eyes, nose, mouth, and ear as well as being accompanied by decreased blood plasma volume. All of this can lead to Dengue Shock Syndrome which has a high mortality rate.

The attachment of the viral particle to the host cell is moved along by the DENV E protein found on the viral surface. DENV prM protein is important in the formation and maturation of the viral particle.

The reasons that some suffer worse than others is due to the different strains of the virus that people contract as well as their immune backgrounds. Generally the virus is diagnosed clinically but Rapid Diagnostic Test kits provide useful for diagnosing in rural areas without laboratory facilities. There is also the Platelia Dengue NS1 Ag assay which rapidly detects DENV before antibodies appear.

There is no proven vaccine although there are many vaccine development programs. One of those, set up in 2003, is the Pediatric Dengue Vaccine whose goal it is to accelerate the development and introduction of dengue vaccines that are affordable and accessible. Typical treatment is timely supportive therapy that tackles circulatory shock due to decreased blood plasma. Lots of liquids are recommended to prevent dehydration in moderate to severe cases. In severe cases intravenous fluids may be necessary to prevent dehydration and a platelet transfusion may also be needed if significant loss of blood is occurring. Aspirin should be avoided as these drugs may worsen the bleeding tendency associated with some of these infections.

The first epidemics occurred in Asia, Africa, and North America in the 1780s shortly after the diseased was identified. In Southeast Asia DHF became a leading cause of death among children in the region. By the 1990s, after Malaria, Dengue had become one of the most important mosquito-borne disease affecting humans with about 40 million cases each year. Major outbreaks occur every five or six months. This cyclical nature of the disease is thought to be due to cross-immunity for all four strains in people who have had dengue. Once cross-immunity wears off the people are more susceptible to transmission leading to outbreaks.

In 2002 a outbreak in Rio De Janeiro killed sixteen people and affected over a million. Singapore has a reported 4,000-5,000 reported cases each year. In Puerto Rico, in 2010, a occurring outbreak has 5382 confirmed infections and 20 deaths.

Along with mosquitoes the disease can be transmitted via infected blood products. The disease spread globally during World War II due to population movements. In regards to war the United States has researched Dengue fever as a potential biological weapon.