Dengue is endemic in tropical regions of the world, at latitudes from around 35 ° north to 35 ° south. Outbreaks are more prevalent in Southeast Asia but may also appear in the Caribbean, as in Puerto Rico and the US Virgin Islands, Oceania and the Indian subcontinent; more recently the incidence of dengue increased in Central and South America. Every year around 100 to 200 cases are reported in the United States, brought by tourists, but it is estimated that there are between 50 and 100 million cases worldwide, with around 20,000 deaths.
The causative organism, a flavivirus with 4 serogroups, is transmitted by the bite of Aedes mosquitoes. The virus circulates in the blood of infected humans for 2 to 7 days and the Aedes mosquito can become infected with the virus when it feeds on humans during this period.
Signs and symptoms
After an incubation period of 3 to 15 days, the patient suddenly presents with fever, chills, headache, retroorbital pain during eye movements, low back pain and severe prostration. During the first hours, the patient has very severe pain in the legs and joints, responsible for the traditional name of "bone breaker fever". The temperature rises rapidly to 40 ° C, with relative bradycardia. Bulbar and conjunctival injection and erythema or malignant rash of transient pale pink color (particularly in the face) may also be found. Often, the cervical, epitrochlear and inguinal lymph nodes are enlarged.
Fever and other symptoms persist for 48 to 96 hours and then a rapid decrease is observed with heavy sweating. Next, patients feel good for about 24 hours, and the fever may recur after this period (saddle pattern), with a maximum lower value than in the first episode. Simultaneously, a maculopapular rash appears that pales compression and extends from the trunk to the limbs and face.
Odynophagia or gastrointestinal symptoms (nausea, vomiting), and bleeding symptoms may occur. Some patients develop dengue hemorrhagic fever.
Dengue hemorrhagic fever is a variety of dengue that occurs mostly in children <10 years living in areas where dengue is endemic. The disease requires prior infection with dengue virus. It is an immunopathological disease; Dengue virus immune complexes with antibodies trigger the release of vasoactive mediators by macrophages. Mediators increase vascular permeability, causing vascular losses, hemorrhagic manifestations, hemoconcentration, and serous effusions, which lead to circulatory collapse (i.e. dengue shock syndrome).
Marked leukopenia and thrombocytopenia are observed in this disease. Diagnostic tests consist of serological tests in the acute and convalescence period, antigen detection and blood PCR.
Dengue treatment is symptomatic. Paracetamol may be indicated, but NSAIDs, including aspirin, should be avoided due to the risk of bleeding. Aspirin increases the risk of Reye's syndrome in children and should be avoided for that reason.
People who live in endemic areas should try to prevent mosquito bites. Dengue patients should avoid the transmission of the disease by mosquitoes by staying under mosquito nets until the resolution of the second febrile episode.
Several vaccine candidates are currently under investigation.
What are the key concepts about dengue?
• Dengue virus is transmitted by the bite of Aedes mosquitoes.
• Dengue fever usually causes sudden fever, severe retroorbital headache, myalgias, adenopathy, a characteristic rash and extreme pain in the legs and joints during the first hours.
• Dengue fever can cause a potentially lethal hemorrhagic fever, with a tendency to bleeding and shock (dengue hemorrhagic fever).
• Suspect dengue fever if patients living in or endemic areas or have traveled to them have typical symptoms; diagnose by serological tests, antigen tests, or by blood PCR.
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