Controlling the spread of dengue

Dengue prevention and cure

One should suspect dengue if an individual suddenly fever with severe headache, muscle and joint pains (also known as myalgias and arthralgias, the severe pain that is experienced is often called break-bone fever or bonecrusher disease) and rashes.

Signs and symptoms

With regards to dengue rashes, they often come as bright red petechia and usually appears first on the lower limbs and the chest. In some patients, they spread to cover most of the body. There may also be gastritis with some combination of associated abdominal and pain, nausea, vomiting or diarrhea.

Some cases develop much milder symptoms which can, when no rash is present, be misdiagnosed as influenza or other viral infection. Because of this, travelers from tropical areas may inadvertently pass on dengue in their home countries, having not been properly diagnosed at the height of their illness.

Dengue carriers can pass on the infection only through mosquitoes or blood products and only while they are still febrile. A classic dengue fever lasts about seven to eight days with a smaller peak of fever at the trailing end of the disease. This is usually referred to as the biphasic pattern. Clinically, the platelet count will drop until the patient’s temperature is normal.

In more severe cases, the patient will also experience higher feve, haemorhagic phenomena, thrombocytopenia, and haemoconcentration while a small proportioof cases may lead to dengue shock syndrome, a condition that has a high mortality rate.

 Prevention measures

At the moment there is no commercially available vaccine for the dengue flavivirus, the culprit behind dengue. However, there is an ongoing vaccine development program called the Pediatric Dengue vaccine Initiative. Set up in 2003, the program aims to accelerate the development and introduction of dengue vaccines that are affordable and accessible to poor children in endemic countries. In fact, Thai researchers are testing a dengue fever vaccine on 3,000 to 5,000 human volunteers after successfully conducted tests on animals and a small group of human volunteers while a number of other vaccine candidates are entering phase I or II testing.

Mosquito control

Primary prevention of dengue mainly resides in mosquito control; for example, the elimination or reduction of the mosquito vector for dengue.

This is why public spraying for mosquitoes is the most important aspect of this vector. Application of larvicides to standing water is more effective in the long-term control of mosquitoes. Initiatives to eradicate pools of standing water (such as flowerpots) have proven useful in controlling mosquito-borne diseases. Promising new techniques have been recently reported from Oxford University on rendering the Aedes mosquito pest sterile.

In 1998, scientists from the Queensland Institute of Research in Australia and Vietnam’s Ministry of Health had introduced a scheme that encouraged children to place a water bug, a crustacean called Mesocyclops, in water tanks and discarded containers where the mosquito particularly the Aedes Aegypti, was known to thrive.

Although not as effective as using pesticides and require participation of the community, this is viewed as being more cost-effective and more environment-friendly.

As for individuals, personal prevention should include the use of mosquito nets, repellents containing NNDB or DEET, covering exposed skin, use of DEET-impregnated bednets, and avoiding endemic areas.