WHODengue is transmitted by the bite of a mosquito infected with one of the four dengue virus serotypes. It is a febrile illness that affects infants, young children and adults with symptoms appearing 3-14 days after the infective bite.Dengue is not transmitted directly from person-to-person and symptoms range from mild fever, to incapacitating high fever, with severe headache, pain behind the eyes, muscle and joint pain, and rash. There is no vaccine or any specific medicine to treat dengue. People who have dengue fever should rest, drink plenty of fluids and reduce the fever using paracetamol or see a doctor.Severe dengue (also known as dengue hemorrhagic fever) is characterized by fever, abdominal pain, persistent vomiting, bleeding and breathing difficulty and is a potentially lethal complication, affecting mainly children. Early clinical diagnosis and careful clinical management by trained physicians and nurses increase survival of patients.The disease manifests as a sudden onset of severe headache, chills, pain upon moving the eyes, and low backache. Painful aching in the legs and joints (myalgias and arthralgiassevere pain that gives it the nick-name break-bone fever or bonecrusher disease) occurs during the first hours of illness. The temperature rises quickly as high as 40 C, with relative low heart rate (bradycardia) and low blood pressure (hypotension). The dengue rash is characteristically bright red petechiae and usually appears first on the lower limbs and the chest (see figure 2). The glands (lymph nodes) in the neck and groin are often swollen. In some patients, it spreads to cover most of the body. There may also be gastritis with some combination of associated abdominal pain, nausea, vomiting, or diarrhea. Some cases develop much milder symptoms which can be misdiagnosed asinfluenza,chikungunya, or other viral infection when no rash is present. The classic dengue fever lasts about six to seven days, with a smaller peak of fever at the trailing end of the disease (the so-called biphasic pattern). Clinically, the platelet count will drop until the patient's temperature is normal.Recognition of Dengue fever- Sudden onset of high fever- Severe headache (mostly in the forehead)- Pain behind the eyes which worsens with eye movement- Body aches and joint pains- Nausea or vomiting

Figure 2: Typical dengue fever symptoms, patients with dengue fever rashDengue virus infections are sometimes confused withchikungunyaviral infection, because both diseases can present with high temperatures and myalgias (muscle pain) in people living in or returning from tropical areas (see table 1). Although these diseases share similar clinical features, prominent and prolonged joint pains are more consistent withchikungunya, whereas haemorrhage is more common in cases of dengue virus infection.Dengue hemorrhagic fever (DHF) is caused by the same viruses and is characterized by increased vascular permeability, hypovolaemia and abnormal blood clotting mechanisms. DHF is a potentially deadly complication with symptoms similar to those ofdengue fever, but after several days the patient becomes irritable, restless, and sweaty. The illness often begins with a sudden rise in temperature accompanied by facial flush and other flu-like symptoms. The fever usually continues for two to seven days and can be as high as 41C, possibly with convulsions and other complications.In moderate DHF cases, all signs and symptoms abate after the fever subsides. In severe cases, the patient's condition may suddenly deteriorate after a few days of fever; the temperature drops, followed by signs of circulatory failure, and the patient may rapidly go into a critical state of shock. The Dengue Shock Syndrome (DSS) is characterized by bleeding that may appear as tiny spots of blood on the skin (petechiae) and larger patches of blood under the skin (ecchymoses). Minor injuries may cause bleeding (see figure 4). Shock may cause death within 12 to 24 hours. Patients can recover following appropriate medical treatment.The progress towards DHF or DSS occur after 3-5 days of fever (see figure 3). At this time, fever has often come down. This may mislead many of us to believe that the patient is heading towards recovery. In fact, this is the most dangerous period that requires high vigilance from care-givers.ecognition of Dengue Haemorrhagic Fever (DHF)- Symptoms similar to dengue fever plus, any one of the following:- Severe and continuous pain in abdomen- Bleeding from the nose, mouth and gums or skin bruising- Frequent vomiting with or without blood- Black stools, like coal tar- Excessive thirst (dry mouth)- Pale, cold skin- Restlessness, or sleepinessDengue shock syndrome is defined as dengue hemorrhagic fever plus:- Weak rapid pulse- Narrow pulse pressure (less than 20 mm Hg)- Cold, clammy skin and restlessness.Dengue hemorrhagic feverDengue hemorrhagic fever is a severe, potentially deadly infection spread by mosquitos, mainly the speciesAedes aegypti.CausesFour different dengue viruses are known to cause dengue hemorrhagic fever. Dengue hemorrhagic fever occurs when a person is bitten by a mosquito that is infected with the virus.There aremore than 100 million new cases of dengue fever every year throughout the world. A small number of these develop into dengue hemorrhagic fever. Most infections in the United States are brought in from other countries. Risk factors for dengue hemorrhagic fever include having antibodies to dengue virus froman earlierinfection and being younger than 12, female, or Caucasian.SymptomsEarly symptoms of dengue hemorrhagic fever are similar to those of dengue fever. But after several days the patient becomes irritable,restless, and sweaty. These symptoms are followed by ashock-like state.Bleeding appears as tiny spots of blood on the skin (petechiae) and larger patches of blood under the skin (ecchymoses). Minor injuries cancause bleeding.Shockcanlead todeath. If the patient survives, recovery begins after a one-day crisis period.Early symptoms include: Decreased appetite Fever Headache Joint or muscleaches Malaise VomitingAcutephase symptoms include: Restlessness followed by: Ecchymosis Generalized rash Petechiae Worsening of earlier symptoms Shock-like state Cold, clammy extremities SweatingExams and TestsAphysical examinationmay reveal: Enlarged liver(hepatomegaly) Low blood pressure Rash Red eyes Red throat Swollen glands Weak,rapid pulseTests may include: Arterial blood gases Blood tests (find signsof the virus in the blood) Coagulation studies Electrolytes Hematocrit Liver enzymes Platelet count Serum studies from samples taken during acute illness and convalescence (increase intiterto Dengueantigen) Tourniquet test (causes petechiae to form below the tourniquet) X-ray of the chest(may demonstrate pleural effusion)TreatmentBecause Dengue hemorrhagic fever is caused by a virus for which there is no known cure or vaccine, the only treatment is to treat the symptoms. A transfusion of fresh blood orplateletscan correct bleeding problems Intravenous(IV) fluids and electrolytes are also used to correctelectrolyte imbalances Oxygen therapy may be needed to treat abnormally low blood oxygen Rehydration with intravenous (IV) fluids is often necessary to treat dehydration Supportive care in an intensive care unit/environmentOutlook (Prognosis)With early and aggressive care, most patients recover from dengue hemorrhagic fever. However, half of untreated patients who go into shock do not survive.Possible Complications Encephalopathy Liver damage Residual brain damage Seizures ShockWhen to Contact a Medical ProfessionalSeeyour health care provider right away if you have symptoms of dengue fever and have been in an area where dengue fever occurs, andespecially if you have had dengue fever before.PreventionThere is no vaccine to prevent dengue fever. Use personal protection such as full-coverage clothing, mosquito nets, mosquito repellent containing DEET. If possible, travel during times of the day when mosquitos are not so active. Mosquito abatement (control)programs can also reduce the risk of infection.Alternative NamesHemorrhagic dengue; Dengue shock syndrome; Philippine hemorrhagic fever; Thai hemorrhagic fever; Singapore hemorrhagic feverDengue hemorrhagic fever is a severe and sometimes fatal infection that occurs tropical regions. It is most common in Southeast Asia and the western Pacific islands. The disease has been increasing rapidly in Latin America and the Caribbean.The dengue virus is transmitted by mosquitoes. A more severe version of the infection called dengue hemorrhagic fever can involve significant bleeding and a drop in blood pressure that can cause shock and death. This condition is sometimes known as dengue shock syndrome.What Causes Dengue Hemorrhagic Fever?Dengue hemorrhagic fever can occur when a person is bitten by a mosquito and exposed to blood infected with the dengue virus. Those who are repeatedly exposed to the dengue virus often experience more acute symptoms and are at risk for dengue hemorrhagic fever.Who Is at High Risk for Dengue Hemorrhagic Fever?Living in or traveling to Southeast Asia, South and Central America, Sub-Saharan Africa, and parts of the Caribbean can increase your risk of contracting the dengue virus. These patients are also at higher risk: infants and small children the elderly those with compromised immune systemsWhat Are The Symptoms of Dengue Hemorrhagic Fever?Symptoms of the dengue virus generally include: mild, moderate, or high fever headaches nausea vomiting pain in the muscles, bones, or joints rashes on the skinIn the case of dengue hemorrhagic fever, other disturbing symptoms can develop. These may include: restlessness acute fever bleeding or bruising under the skin cold or clammy skinHow Is Dengue Hemorrhagic Fever Diagnosed?Doctors will usually diagnose the type of dengue virus and then begin to look for signs of dengue hemorrhagic fever. Your doctor may do the following: check your blood pressure examine your skin, eyes, and glands perform blood tests and coagulation studies take a chest X-rayIn addition to performing these tests, your doctor may ask you questions about your personal and family medical history. Your doctor may ask about your lifestyle and recent travels. Your doctors may also try to rule out other conditions like malaria that are common in tropical regions.Treatment for Dengue Hemorrhagic FeverIf you have dengue hemorrhagic fever, your doctor will treat the symptoms in order to prevent the condition from becoming more severe. Emergency treatment methods may include: hydration with intravenous (IV) fluids over-the-counter or prescription drugs to manage pain electrolyte therapy blood transfusions careful monitoring of blood pressure oxygen therapy skilled nursing observationAll these methods are aimed at controlling and alleviating the symptoms while helping your body heal naturally. Doctors will continue to monitor your bodys response.What Is The Long-Term Outlook?The prognosis for dengue hemorrhagic fever depends on how early the condition is detected. Patients who receive care in the early stages of dengue infection will often recover. As the patient moves toward a stage of shock, recovery becomes progressively more unlikely. Complications from severe or acute dengue hemorrhagic fever may include seizures, brain damage, and damage to other major organs.How Can I Prevent Dengue Hemorrhagic Fever?Researchers are working on a vaccine to prevent dengue fever. But it is currently unavailable. To protect yourself from mosquito bites, wear clothing that covers your arms and legs. Use mosquito netting and mosquito repellent when traveling in the tropics.Transmission

WHO/TDR/StammersTheAedes aegyptimosquito is the primary vector of dengue. The virus is transmitted to humans through the bites of infected female mosquitoes. After virus incubation for 410 days, an infected mosquito is capable of transmitting the virus for the rest of its life.Infected humans are the main carriers and multipliers of the virus, serving as a source of the virus for uninfected mosquitoes. Patients who are already infected with the dengue virus can transmit the infection (for 45 days; maximum 12) viaAedesmosquitoes after their first symptoms appear.TheAedes aegyptimosquito lives in urban habitats and breeds mostly in man-made containers. Unlike other mosquitoesAe. aegyptiis a day-time feeder; its peak biting periods are early in the morning and in the evening before dusk. FemaleAe. aegyptibites multiple people during each feeding period.Aedes albopictus, a secondary dengue vector in Asia, has spread to North America and Europe largely due to the international trade in used tyres (a breeding habitat) and other goods (e.g. lucky bamboo).Ae. albopictusis highly adaptive and, therefore, can survive in cooler temperate regions of Europe. Its spread is due to its tolerance to temperatures below freezing, hibernation, and ability to shelter in microhabitats.

CharacteristicsDengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death.Dengue should be suspected when a high fever (40C/104F) is accompanied by 2 of the following symptoms: severe headache, pain behind the eyes, muscle and joint pains, nausea, vomiting, swollen glands or rash. Symptoms usually last for 27 days, after an incubation period of 410 days after the bite from an infected mosquito.Severe dengue is a potentially deadly complication due to plasma leaking, fluid accumulation, respiratory distress, severe bleeding, or organ impairment. Warning signs occur 37 days after the first symptoms in conjunction with a decrease in temperature (below 38C/100F) and include: severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums, fatigue, restlessness and blood in vomit. The next 2448 hours of the critical stage can be lethal; proper medical care is needed to avoid complications and risk of death.TreatmentThere is no specific treatment for dengue fever.For severe dengue, medical care by physicians and nurses experienced with the effects and progression of the disease can save lives decreasing mortality rates from more than 20% to less than 1%. Maintenance of the patient's body fluid volume is critical to severe dengue care.ImmunizationThere is no vaccine to protect against dengue. However, major progress has been made in developing a vaccine against dengue/severe dengue. Three tetravalent live-attenuated vaccines are under development in phase II and phase III clinical trials, and 3 other vaccine candidates (based on subunit, DNA and purified inactivated virus platforms) are at earlier stages of clinical development. WHO provides technical advice and guidance to countries and private partners to support vaccine research and evaluation.

Symptoms of Dengue FeverSymptoms, which usually begin four to six days after infection and last for up to 10 days, may include Sudden, high fever Severe headaches Pain behind the eyes Severe joint and muscle pain Nausea Vomiting Skin rash, which appears three to four days after the onset of fever Mild bleeding (such a nose bleed,bleeding gums, or easy bruising)Sometimes symptoms are mild and can be mistaken for those of thefluor anotherviral infection. Younger children and people who have never had the infection before tend to have milder cases than older children and adults. However, serious problems can develop. These include dengue hemorrhagic fever, a rare complication characterized by high fever, damage to lymph and blood vessels, bleeding from the nose and gums, enlargement of theliver, and failure of the circulatory system. The symptoms may progress to massive bleeding, shock, and death. This is called dengue shock syndrome (DSS).People with weakened immune systems as well as those with a second or subsequent dengue infection are believed to be at greater risk for developing dengue hemorrhagic fever.