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Indonesia, as one of the largest countries in the world, spreading over more than 5.000 kilometers from east to west and containing over 17.000 islands, is quite vulnerable for a number of disease. The health care system in general is not adequately equipped to deal with many basic situations, which should be a reason to get proper information about common diseases.


Dengue
A largely unknown but important disease

Dengue fever and dengue hemorrhagic fever (DHF) are acute febrile diseases, found in the tropics, with a geographical spread similar to malaria. Caused by one of four closely related virus serotypes of the genus Flavivirus, family Flaviviridae, each serotype is sufficiently different that there is no cross-protection and epidemics caused by multiple serotypes (hyperendemicity) can occur. Dengue is transmitted to humans by the Aedes aegypti (rarely Aedes albopictus) mosquito, which feeds during the day.

Signs and symptoms

This infectious disease is manifested by 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) and 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, which can, 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.


World-wide dengue distribution, 2006. Red: Epidemic dengue. Blue: Aedes aegypti. © CDC, public domain.

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.

Cases of DHF also show higher fever, haemorrhagic phenomena, thrombocytopenia and haemoconcentration. A small proportion of cases lead to dengue shock syndrome (DSS) which has a high mortality rate.

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 mm│ 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

Serology and PCR (polymerase chain reaction) studies are available to confirm the diagnosis of dengue if clinically indicated.

Treatment

The mainstay of treatment is supportive therapy. 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.

Epidemiology

The first epidemics occurred almost simultaneously, in Asia, Africa and North America in the 1780s. The disease was identified and named in 1779. A global pandemic began in Southeast Asia in the 1950s and by 1975 DHF had become a leading cause of death among children in many countries in that region. Epidemic dengue has become more common since the 1980s - by the late 1990s, dengue was the most important mosquito-borne disease affecting humans after malaria, there being around 40 million cases of dengue fever and several hundred thousand cases of dengue hemorrhagic fever each year. In February 2002 there was a serious outbreak in Rio de Janeiro, affecting around one million people but only killing sixteen.

Significant outbreaks of dengue fever tend to occur every five or six years. There tend to remain large numbers of susceptible people in the population despite previous outbreaks because there are four different strains of the dengue virus and because of new susceptible individuals entering the target population, either through childbirth or immigration.

There is significant evidence, originally suggested by S.B. Halstead in the 1970s, that dengue hemorrhagic fever is more likely to occur in patients who have secondary infections by serotypes different from the primary infection. One model to explain this process is known as antibody-dependent enhancement (ADE), which allows for increased uptake and virion replication during a secondary infection with a different strain. Through an immunological phenomena, known as original antigenic sin, the immune system is not able to adequately respond to the stronger infection, and the secondary infection becomes far more serious. This process is also known as superinfection (Nowak and May 1994; Levin and Pimentel 1981).

In Singapore, there are about 4,000-5,000 reported cases of dengue fever or dengue haemorrhagic fever every year. In the year 2003, there were 6 deaths from dengue shock syndrome. It is believed that the reported cases of dengue are an underrepresentation of all the cases of dengue as it would ignore subclinical cases and cases where the patient did not present for medical treatment. With proper medical treatment, the mortality rate for dengue can therefore be brought down to less than 1 in 1000.

Prevention

Vaccine development

There is no commercially available vaccine for the dengue flavivirus. However, one of the many ongoing vaccine development programs is the Pediatric Dengue Vaccine Initiative which was set up in 2003 with the aim of accelerating the development and introduction of dengue vaccine(s) that are affordable and accessible to poor children in endemic countries.[4] Thai researchers are testing a dengue fever vaccine on 3,000-5,000 human volunteers within the next three years after having successfully conducted tests on animals and a small group of human volunteers.[5] and a number of other vaccine candidates are entering phase I or II testing.[6]

Mosquito control

Primary prevention of dengue mainly resides in 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.

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.


All text in this article is available under the terms of the GNU Free Documentation License
Last revised on October 11, 2009
    
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