Dengue Fever and Dengue Hemorrhagic Fever (DHF) are acute febrile (fever) diseases that are found in the tropics.

Dengue is often found in urban areas of developed tropical nations, including Brazil, Singapore, and Taiwan.

Symptoms

The symptoms of Dengue include:

• Abdominal pain
• Diarrhea
• Fever, with a sudden onset
• Nausea
• Severe headache
• Severe muscle and joint pains (myalgias and arthralgias—severe pain gives it the name break-bone fever or bonecrusher disease)
• Skin rashes, which is typically bright red and usually appears first on the lower limbs and the chest. This rash can spread to cover most of the body
• Vomiting

Some people develop milder symptoms, and sometimes no skin rash appears, and this can lead to misdiagnosis.

The classic dengue fever lasts about six to seven days, with a smaller peak of fever at the trailing end of the disease (the so-called "biphasic pattern"). Clinically, the platelet count will drop until the patient's temperature is normal.

In rare cases, the symptoms of Dengue may be far more serious, and include:

• Haemorrhagic phenomena,
• Higher fever,
• Thrombocytopenia

In rare cases, Dengue may progress toe Dengue Shock Syndrome (DSS), the symptoms of which include any or all of those listed above as well as:

• Cold, clammy skin,
• Restlessness,
• Weak rapid pulse

DSS is often fatal.

Causes

Dengue is caused by one of four closely related Flaviviridae viruses. Each type of virus is sufficiently different that there is no cross-protection. In other words, a person can contract Dengue from each of the virus types. Immunity from one does not protect you from the others.
Because of this, Dengue can cause hyperendemicity, which occurs when multiple epidemics occur at the same time, each caused by one of the four different viruses.

Dengue Transmission

Dengue may be transmitted to humans, or between humans, in a variety of ways:

• Mosquito Bite: In almost every case, Dengue is transmitted to humans by the Aedes aegypti mosquito, which feeds during the day. In rare cases, the Aedes albopictus mosquito can transmit the disease to humans.
• Blood Transfusion: Patients with Dengue can also pass the infection onto other people if they donate blood while they are still febrile (suffering from fever).

Treatment

The main treatment for Dengue sufferers is the following supportive therapies:

• Acetaminophen preparations to deal with headache and pain.
• Increased Fluid Intake: Increased oral fluid intake is recommended to prevent dehydration. Supplementation with intravenous fluids may be necessary, especially if the sufferer is unable to maintain oral intake.
• Blood and/or Platelet Transfusions: A platelet transfusion may also be required if the sufferers platelet count drops below 20,000, or if there is significant bleeding. Gastrointestinal bleeding may also require a platelet or blood transfusion.

WARNING: The following medications must be avoided by Dengue sufferers because they may aggravate any bleeding:

• Aspirin,
• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs),

Prevention and Control

The following techniques are used to attempt to prevent and control Dengue:

• Insect Control: the primary prevention measure for Dengue is mosquito eradication and control, which involves emptying pools of standing water (such as in the bases of flowerpots), spraying for mosquitoes, and applying larvicides (such as Abate) to standing water. A fresh water crustacean, called Mesocyclops, can also be placed in water tanks and pools, and this organism eats and destroys the mosquito larvae. This solution is cheaper and far more environmentally friendly than pesticides, though not quite as effective. It also requires the ongoing participation of the local community.
• Personal Protection: includes a range of measures, including covering exposed skin, using mosquito nets and screens on doors and windows, using insect repellents containing NNDB or DEET, using DEET-impregnated mosquito nets, and avoiding areas where Dengue mosquitoes are common.
• Vaccine Development: while there is no commercially available vaccine for the Dengue flavivirus, a great deal of research is being conducted into developing and trialing various possible vaccines that are showing promising results.

Further research is constantly being conducted into a range of antiviral approaches to attack the Dengue virus directly, and this research may deliver better treatments or even eradication of the viruses in the future.