Dengue Fever
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Dengue virus is an arbovirus transmitted by aedes mosquitoes (both Ae. aegypti and Ae. albopiticus). Dengue fever is caused by four serologically distinct, but closely related Dengue viruses: dengue virus (DENV) 1, 2, 3, and 4 of the Flaviviridae family. Dengue fever is an emerging pandemic that has spread globally during the past 30 years as a result of changes in human ecology. Dengue haemorrhagic fever (DHF) is a potentially deadly complication that has become a leading cause of hospitalization and death among children in Asia and Africa. There is good evidence that sequential infection with the different serotypes of dengue virus increases the risk of more severe disease that can result in dengue shock syndrome (DSS) and death.
Infected humans are the main carriers and multipliers of the virus, serving a source of the virus for uninfected Aedes aegypti mosquitoes which maintain the urban dengue transmission cycle. The virus circulates in the blood of infected human for 2-7 days, at approximately the same time that they have a fever. A sylvatic transmission cycle has been documented in West Africa where DENV-2 has been found in monkeys. There is no evidence of person-to-person transmission.
DENV is frequently transported from one place to another by infected travelers; when susceptible vectors are present in these new areas, there is the potential for local transmission to be established.
Case DefinitionDengue Fever Suspected case: Any person with acute febrile illness of 2-7 days duration with 2 or more of the following: headache, retro-orbital pain, myalgia, arthralgia, rash, haemorrhagic manifestations, leucopenia.
Dengue Fever Confirmed case: A suspected case with laboratory confirmation (positive IgM antibody, four-fold or greater rise in IgG antibody titres, positive PCR or viral isolation).
Dengue Haemorrhagic Fever: A probable or confirmed case of dengue with bleeding tendencies as evidenced by one or more of the following: positive tourniquet test; petechieae, ecchymoses or purpura; bleeding: mucosa, gastrointestinal tract, injection sites or other; haematemesis or melaena; and thrombocytopenia (100,000 cells or less per mm3) and evidence of plasma leakage due to increased vascular permeability, manifested by one or more of the following: 20% rise in average haematocrit for age and sex, 20% drop in haematocrit following volume replacement therapy compared to baseline, signs of plasma leakage (pleural effusion, ascites, hypo-proteinaemia).
Dengue Shock Syndrome: All the above criteria, plus evidence of circulatory failure manifested by rapid and weak pulse, and narrow pulse pressure (≤ 20 mm Hg) or hypotension for age, cold, clammy skin and altered mental status.
Laboratory Investigations
- Reverse Transcriptase–Polymerase Chain Reaction (RT–PCR)
- Rapid Tests for Dengue NSI antigen
Serological methods, such as Enzyme-Linked Immunosorbent Assays (ELISA) for IgM and IgG anti-dengue antibodies FBP
Management There is no specific treatment for dengue, but appropriate medical care frequently saves the lives of patients with dengue haemorrhagic fever.
Non-Pharmacological Treatment
- No specific treatment is available for Dengue fever.
Pharmacological Treatment:
A: paracetamol (PO/IV) 15mg/kg 8hourly for 3days
A: Maintainance fluid (Ringers lactate, NS) intravenously if one cannot take enough fluid orally
B: Blood transfusion and clotting factors.
B: Oxygen and manage hypoglycaemia if present
Note:
- No antibiotics are of proven value.
- Children below 12 years require close monitoring for dangerous form.
- Steroids should not be used.
- Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) such as ibuprofen and aspirin should be avoided. These anti-inflammatory drugs act by thinning the blood, and in a disease with risk of hemorrhage, blood thinners may exacerbate the prognosis .
Prevention
At present, the only method of controlling or preventing dengue virus transmission is to combat the vector mosquitoes using environmental management and chemical methods.
- Prevent dengue by avoiding mosquito bites by Aedes. aegypti and Aedes. albopictus bite during the day and night (using mosquito repellant, bed nets and removing reservoirs).
- All four dengue viruses are spread primarily through the bite of an infected Aedes mosquito.
- A dengue vaccine is available for use in some parts of the world.
Public Health Control Measures
- Wear full sleeve clothes and long dresses to cover the limbs
- Use mosquito repellents
- Use mosquito nets – to protect babies, old people and others, who may rest during the day. Effectiveness of such nets can be improved by treating them with permethrin (pyrethroid insecticide). Curtains (cloth or bamboo) can also be treated with insecticide and hung at windows or doorways, to repel or kill mosquitoes