Dengue fever and dengue hemorrhagic fever (DHF) are acute febrile diseases, found in the tropics, with a geographical spread similar to malaria. Dengue is transmitted to humans by the Aedes aegypti (rarely Aedes albopictus) mosquito, which feeds during the day.
Signs and symptoms
* A sudden onset of fever, with severe headache, muscle and joint pains (myalgias and arthralgias - severe pain gives it the name break-bone fever or bonecrusher disease)
* Rashes; the dengue rash is characteristically bright red petechia and usually appears first on the lower limbs and the chest - in some patients, it spreads to cover most of the body.
* There may also be gastritis with some combination of associated abdominal pain, nausea, vomiting or diarrhea.
Some cases develop much milder symptoms, when no rash is present, be misdiagnosed as influenza or other viral infection. Thus, travelers from tropical areas may inadvertently pass on dengue in their home countries, having not been properly diagnosed at the height of their illness. Patients with dengue can only pass on the infection through mosquitoes or blood products while they are still febrile.
The classic dengue fever lasts about six to seven days, with a smaller peak of fever at the trailing end of the fever (the so-called "biphasic pattern"). Clinically, the platelet count will drop until the patient's temperature is normal.
Diagnosis
The diagnosis of dengue is usually made clinically. The classic picture is high fever with no localising source of infection, a petechial rash with thrombocytopenia and relative leukopenia.
There exists a WHO definition of dengue haemorrhagic fever that has been in use since 1975; all four criteria must be fulfilled:
* Fever
* Haemorrhagic tendency (positive tourniquet test, spontaneous bruising, bleeding from mucosa, gingiva, injection sites, etc.; vomiting blood, or bloody diarrhea)
* Thrombocytopaenia (<100,000 platelets per mm³ or estimated as less than 3 platelets per high power field)
* Evidence of plasma leakage (hematocrit more than 20% higher than expected, or drop in haematocrit of 20% or more from baseline following IV fluid, pleural effusion, ascites, hypoproteinaemia)
Dengue shock syndrome is defined as dengue haemorrhagic fever plus:
* Weak rapid pulse,
* Narrow pulse pressure (less than 20 mm Hg)
or,
* Hypotension for age;
* Cold, clammy skin and restlessness.
* Treatment
Increased oral fluid intake is recommended to prevent dehydration. If the patient is unable to maintain oral intake, supplementation with intravenous fluids may be necessary to prevent dehydration and significant hemoconcentration. A platelet transfusion is rarely indicated if the platelet level drops significantly (below 20,000) or if there is significant bleeding.
The presence of melena may indicate internal gastrointestinal bleeding requiring platelet and/or red blood cell transfusion.
It is very important to avoid Aspirin and non-steroidal anti-inflammatory medications. These drugs are often used to treat pain and fever, but in this case, they may actually aggravate the bleeding tendency associated with some of these infections. If dengue is suspected, patients should receive instead acetaminophen preparations to deal with these symptoms
Prevention
1. Mosquito control
* Eliminating or reducing the mosquito vector for dengue.
* Public spraying for mosquitoes is the most important aspect of this vector.
* Application of larvicides such as Abate® to standing water is more effective in the long term control of mosquitoes.
* Initiatives to eradicate pools of standing water (such as in 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.
Recently, researchers at the Federal University of Minas Gerais, in Brazil, have developed an world awarded new technology to monitor and control the mosquito, using traps, chemical attractants, handheld computers and GPS georeferenced maps. The MI Dengue system can show precisely where the mosquitoes are inside the urban area, in a very short period of time.
2. Personal protection
Personal prevention consists of the use of mosquito nets, repellents containing NNDB or DEET, cover exposed skin, use DEET-impregnated bednets, and avoiding endemic areas. This is also important for malaria prevention.
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