Dengue

Dengue is an acute febrile disease caused by infection with a group B arbovirus of four serotypes, transmitted by the bite of infected Aedes aegypti and Aedes albopictus mosquitoes. Endemic throughout the tropics and subtropics, uncomplicated dengue is rarely fatal, although return to normal health after an attack may take several weeks. It does not always have a benign course, however, and can be complicated by hemorrhagic manifestations (hemorrhagic dengue) and circulatory collapse (dengue shock syndrome) with a potentially fatal outcome unless facilities are available for the urgent medical treatment of those affected.

Typical uncomplicated dengue has an incubation period of 3 to 15 days and is characterized by abrupt onset of chills, headache, lumbar backache, and severe prostration. Body temperature rises rapidly, perhaps reaching as high as 40°C; bradycardia (slow heart rate) and hypotension (low blood pressure) accompany the high fever. Conjunctival injection, lymph node enlargement, and a pale, pink rash, especially noticeable on the face, are usually present during this first phase of the disease. In classical dengue, the fever lasts for 48 to 96 hours initially, subsides for 24 hours or so, and then returns (saddleback fever), although the peak of temperature is usually lower in the second phase than in the first. A characteristic red rash appears in the second phase, usually covering the trunk and extremities, but sparing the face. The fever, rash, and headache, together with the other pains, are known as the dengue triad. The acute illness ends in 8 to 10 days, and one attack confers immunity to the particular dengue subtype.

Hemorrhagic dengue usually strikes children under the age of 10 and has its highest mortality rate in infants under the age of 1 year. It is more likely to occur when type 2 dengue virus infection follows an earlier type 1 infection in the same individual or when subgroup-specific antibodies have been acquired transplacentally from an immune mother, a phenomenon known as enhancement. Signs of this ominous complication usually occur between the second and the sixth day of the illness and include sudden collapse with a rapid pulse of low volume; cyanosis (blue discoloration) of lips, ears, and nail beds; and cold, clammy extremities while the trunk remains warm. Nosebleeds, the appearance of spontaneous bruising, prolonged bleeding from injection sites, and bleeding from both the upper and lower gastrointestinal tract signal the gross disturbances of blood coagulation mechanisms that occur in this form of the disease.

The world dengue comes from the Spanish, a homonym for the Swahili Ki denga pepo (a sudden cramplike seizure caused by an evil spirit); it was introduced into English medical usage during the Spanish West Indies epidemic of 1827 and 1828. The synonym breakbone fever dates from Philadelphia in 1780, and the term knokkel-koorts comes from Bata-via about the same year. All of these terms refer to some characteristic of the disease, either its sudden onset or the severity of its musculoskeletal pain, or both.

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