Dengue

DengueDefinitionDengue fever, also known asbreakbone fever, is amosquito-bornetropical diseasecaused by the dengue virus.

Dengue is transmitted by several species ofmosquitowithin thegenusAedes, principallyA. aegypti.ClassificationGrade 1- presence only of easy bruising or a positive tourniquet test in someone with feverGrade II- presence of spontaneous bleeding into the skin and elsewhereGrade III- clinical evidence of shockGrade IV- shock so severe that blood pressure andpulsecannot be detected.

*Grades III and IV are referred to as "dengue shock syndrome".Signs and SymptomsWhen symptoms do occur, they usually begin 4 to 10 days after you are bitten by an infected mosquito. Signs and symptoms of dengue fever most commonly include:Fever, as high as 106 F (41 C)HeadachesMuscle, bone and joint painPain behind your eyesYou might also experience:Widespread rashNausea and vomitingRarely, minor bleeding from your gums or nose

Signs and SymptomsMost people recover within a week or so. In some cases, symptoms worsen and can become life-threatening. Blood vessels often become damaged and leaky. And the number of clot-forming cells (platelets) in your bloodstream drops. This can cause:Bleeding from your nose and mouthSevere abdominal painPersistent vomitingBleeding under the skin, which might look like bruisingProblems with your lungs, liver and heart

Pathophysiology

Risk FactorsFactors that put you at greater risk of developing dengue fever or a more severe form of the disease include:Living or traveling in tropical areas.Being in tropical and subtropical areas increases your risk of exposure to the virus that causes dengue fever. Especially high-risk areas are Southeast Asia, the western Pacific islands, Latin America and the Caribbean.Prior infection with a dengue fever virus.Previous infection with a dengue fever virus increases your risk of having severe symptoms if you're infected again.

ComplicationsThe complications of dengue fever are usually associated with the more severe forms of dengue fever, hemorrhagic and shock syndrome. The most serious complications, although infrequent, are as follows:dehydration;bleeding (hemorrhage);low platelets;low blood pressure(hypotension);bradycardia;liver damage;neurological damage (seizures, encephalitis);and death.

DiagnosisA probable diagnosis is based on the findings of fever plus two of the following:nauseaand vomiting, rash, generalized pains,low white blood cell count, positivetourniquet test, or any warning sign in someone who lives in anendemicarea. Warning signs typically occur before the onset of severe dengue.The tourniquet test, which is particularly useful in settings where no laboratory investigations are readily available, involves the application of ablood pressure cuffat between thediastolicand systolic pressure for five minutes, followed by the counting of anypetechial hemorrhages; a higher number makes a diagnosis of dengue more likely with the cut off being more than 10 to 20 per 1inch2(6.25cm2).Drugs and TreatmentsNo specific treatment for dengue fever exists. Your doctor may recommend that you drink plenty of fluids to avoid dehydration from vomiting and high fever. Acetaminophen (Tylenol, others) can alleviate pain and reduce fever. Avoid pain relievers that can increase bleeding complications such as aspirin, ibuprofen (Advil, Motrin IB, others) and naproxen sodium (Aleve, others).If you have severe dengue fever, you may need:Supportive care in a hospitalIntravenous (IV) fluid and electrolyte replacementBlood pressure monitoringTransfusion to replace blood loss

Aspirin, other salicylates, and nonsteroidal anti-inflammatory drugs (NSAIDs) should be avoided.PrognosisThe mortality rate for dengue infection is 0.8% to 2.5%. Children are at an increased risk of severe infection and death compared to adults; however, severe infection in adults is increasingly being reported.The risk of a child aged 1 to 5 years dying from dengue infection is fourfold higher compared to children aged 11 to 15 years.Even though dengue haemorrhagic fever and dengue shock syndrome are uncommon in adults, a higher morbidity and mortality rate has been reported, especially in older people, which is related to an increased risk of organ impairment.Recurrence is possible with a different dengue virus serotype, leading to secondary dengue infection. Third and fourth recurrences of clinical infection can also occur, but the clinical impact is not very clear. Once immunity has developed to all 4 serotypes, lifelong immunity to each serotype occurs.