What is classical dengue fever? dengue fever vaccine? dengue fever

 Classical Dengue Fever

Classical dengue fever or”break-bone fever” is an acute viral infection, caused by at least 4 serotypes(1,2,3 and 4) of dengue virus. Dengue fever can occur epidemically or endemically. Epidemics may be explosive and often start during the rainy season when the breeding of the vector mosquitoes (e.g., Aedes aegypti) is generally abundant. Temperature also plays an important role in the transmission of dengue virus by mosquitoes. Mosquitoes kept at 26 C fail to transmit DEN-2 virus. Hence, the low incidence of DHF in certain seasons could be explained by this observation.
The reservoir of infection is both man and mosquito.

Transmission:

 The transmission cycle is “Man-mosquito-Man”. Aedes aegypti is the main vector. The Aedes mosquito becomes infective by feeding on a patient from the day before onset to the 5th day of illness. After an extrinsic incubation period of 8 to 10 days, the mosquito becomes infective, and is able to transmit the infection. Once the mosquito becomes infective, it remains so for life.Transovarian transmission of dengue virus has been demonstrated in laboratory.All ages and both sexes are susceptible to dengue fever. Children usually have a milder disease than adults.

Incubation period:

The illness is characterised by an incubation period of 3 to 10 days(commonly 5-6 days).

Signs and symptoms:

the onset is sudden with chills and high fever, intense headache, muscle and joint pains which prevent all movement. Within 24 hours retro-orbital pain, particularly on eye movements or eye pressure and photophobia develops. Other common symptoms include extreme weakness, anorexia, constipation, altered taste sensation, colicky pain and abdominal tenderness, dragging pain in inguinal region, sore throat and general depression. Fever is usually between 39 C and 40 C. The skin eruptions appears in 80% of cases during the remission or during second febrile phase, which lasts for 1-2 days. The rash is accompanied by similar but milder symptoms. The rash may be diffuse flushing phase, mottling or fleeting pin-point eruptions on the face, neck and chest during during the first half of the febrile period and a conspicuous rash. It starts on the chest and trunk and may spread to the extremities and rarely to the face. It may be accompanied by itching and hyperaesthesia. The rash lasts for 2 hours to several days. Fever lasts for about 5 days, rarely more than 7 days after which recovery is usually complete although convalescence may be protracted. The case fatality is exceedingly low.

Treatment:

The management of dengue fever is symptomatic and supportive. Bed rest is advisable during the acute febrile phase. Antipyretics or sponging are required to keep the body temperature below 40 C.Oral fluid and electrolyte therapy is recommended for patients with excessive sweating, vomiting or diarrhoea.Aspirin should be avoided, particularly in areas where DHF is endemic, since it may cause gastritis, bleeding and acidosis.


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