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Health

Dengue and Dengue Hemorrhagic Fever

Dengue is caused by any one of four closely related viruses that do not provide cross-protective immunity; a person can be infected as many as four times, once with each serotype. Dengue viruses are transmitted from person to person by the Aedes aegypti mosquito in the domestic environment.

Clinical Diagnosis Dengue
Classic dengue fever is characterised by acute onset of high fever, frontal headache, retro-orbital pain, myalgias, arthralgias, nausea, vomiting, and often a maculopapular rash. In addition, many patients may notice a change in taste sensation. Symptoms tend to be milder in children than in adults, and the illness may be clinically indistinguishable from influenza, measles, or rubella. The disease manifestations can range in intensity from inapparent illness to the symptoms described. The acute phase of up to one week is followed by a one- to two-week period of convalescence which is characterised by weakness, malaise and anorexia. Treatment emphasises relief of these symptoms.

Dengue Hemorrhagic Fever/Dengue Shock Syndrome
During the first few days of illness, dengue hemorrhagic fever (DHF), a severe and sometimes fatal form of dengue, may resemble classic dengue or other viral syndromes. Patients with DHF may have fever lasting two to seven days and a variety of nonspecific signs and symptoms. At about the time the fever begins to subside, the patient may become restless or lethargic, show signs of circulatory failure, and experience hemorrhagic manifestations. The most common of these manifestations are skin hemorrhages but may also include epistaxis, bleeding gums, hematemesis, and melena. The condition of these patients may rapidly evolve into dengue shock syndrome (DSS), which, if not immediately corrected, can lead to profound shock and death. Advance warning signs of DSS include severe abdominal pain, protracted vomiting, marked change in temperature (from fever to hypothermia), or change in mental status (irritability or obtundation). Early signs of DSS include restlessness, cold clammy skin, rapid weak pulse, and narrowing of pulse pressure and/or hypotension. Fatality rates among those with DSS may be as high as 44 per cent. DHF/DSS can occur in children and adults.

Treatment
Fortunately, DHF/DSS can be effectively managed by fluid replacement therapy, and if diagnosed early, fatality rates can be kept below one per cent. Once a person acquires dengue, the key to survival is early diagnosis and appropriate treatment.

To manage the pain and fever, patients suspected of having a dengue infection should be given acetaminophen preparations rather than aspirin, because the anticoagulant effects of aspirin may aggravate the bleeding tendency associated with some dengue infections.

Epidemiology
A dengue epidemic requires the presence of 1) the vector mosquito (Aedes aegypti), 2) the virus, and 3) a large number of susceptible human hosts. Outbreaks may be explosive or progressive, depending on the density and susceptibility of the vector, the strain of dengue virus, the immune level in the human population, and the amount of vector-human contact. Dengue should be considered as the possible etiology where influenza, rubella, or measles is suspected in a dengue-receptive area.

Predicting epidemics of dengue and DHF is difficult but, as noted previously, the frequency of epidemic disease has increased significantly in the past 20 years. This is likely due to increased air travel, which provides the ideal mechanism for dengue viruses to be carried around the world into areas where Aedes aegypti occurs. This rapid movement of travelers around the world is also the reason that dengue infections may be detected in virtually any part of the world.

Source: Yahoo Health