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Dengu Fever Fact Sheet
Introduction
Dengue fever is a disease caused by infection with a type of
virus called Flavivirus. There are four different subtypes of
this virus producing varying manifestations of the disease.
The disease is spread through the bites of mosquitoes
belonging to the Aedes egypti species. The disease is
essentially a tropical one and is endemic in large parts of
Latin and South America. Of late, its incidence has been on
the increase in Asian countries such as India.
Cause and Pathogenesis
Dengue fever is transmitted to humans by the bite of the
infected Aedes egypti mosquito. The Aedes mosquito breeds in
relatively fresh water, lives close to human habitations and
bites during the day. The incubation period between the bite
and the onset of symptoms is usually two to seven days. The
Aedes mosquito is also responsible for the spread of diseases
such as yellow fever and Chikungunya virus fever.
Symptoms and Signs
A large number of infections may be sub-clinical, that is, the
patients may not even be aware that they have had the disease.
The infection usually manifests itself as fever with severe
body pain or myalgia. There may be an associated rash over
parts of the body. The body pain is so intense that this
disease has been called break-bone fever. Quite often, the
disease makes nofurther progress and the patients recover.
However, some patients may develop involvement of either of
the two dreaded syndromes in Dengue - bleeding (called DHF or
Dengue Hemorraghic Fever) or involvement of the brain with
altered consciousness (encephalitis). Fatalities are higher
among patients in whom these complications are present. Joint
pain is another symptom though there may not be true
arthritis. Associated symptoms include severe headache,
vomiting, and photophobia. Examination of the patient may
reveal few findings such as a rash and pain on palpation of
the muscles. These symptoms usually last for a period of two
to five days and most patients who do not have complications
recover completely.
The risk of complications appears to be greater in children,
particularly the risk of bleeding and DHF with its high
fatality rate. Some patients may also go into shock, a
condition known as Dengue Shock Syndrome (DSS). This too
carries a higher risk of mortality.
Investigations and Diagnosis
The diagnosis of dengue is based on the clinical presentation,
knowledge of the area in which the person lives, and
laboratory investigations. Blood tests may show a low white
blood cell count, a low platelet count, and elevation of
certain enzymes.
The definitive diagnosis is, however, made by isolating the
virus in the blood of the individual during the acute phase of
the disease or by detecting antibodies to the virus in the
blood. Antigen detection is also possible. A rise in the
antibody titre is a useful method of diagnosis. Investigations
also need to be done to rule out other likely causes of fever
such as malaria, and leptospirosis.
Treatment and Prognosis
Treatment is usually supportive and symptomatic. Analgesics,
anti-pyretics, and broad-spectrum antibiotics are used during
the acute phase to minimise the risk of secondary infection.
In cases of bleeding, blood transfusions are required. Shock,
if present, needs to be aggressively treated with fluids,
oxygen, and close monitoring. Most patients will recover
without any sequel. The overall mortality rate with effective
treatment is close to 1% but this may be higher in children.
Prevention
Control and elimination of mosquito population is the best
method of prevention. A vaccine is in the late stages of
development but is still not available for commercial use on a
large scale.
Control of the mosquito population reduces the incidence of
dengue, yellow fever, and certain other rare fevers that are
also transmitted by the same species of mosquito.
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