Dengue Fever is an acute viral infection characterized by fever. It is caused by a bite from mosquitoes carrying dengue virus. The primary form of Dengue Fever is characterized by a skin rash and a high fever with severe pain in the head and muscles. Other symptoms may include shaking chills, diarrhea, and vomiting. Bouts of extreme exhaustion may last for months after the initial symptoms.
The secondary forms of this disorder are called Dengue Hemorrhagic Fever and Dengue Shock Syndrome. These usually are caused by a secondary infection with a different type of Dengue virus (Type 2), but may also be caused by the same virus that causes Dengue Fever. Several days after onset other symptoms may include fever, bleeding under the skin, red spots on the legs, and bleeding into the intestines. A marked fall in blood pressure (shock) occurs in very severe cases.
Dengue Fever is a disorder transmitted by female mosquitoes (Aedes aegypti and Aedes albopictus) carrying dengue virus. The disorder is characterized by a sudden onset of symptoms. There is an incubation period of 5 to 8 days after the mosquito bite occurs. The patient has chills or chilly sensations, a fever, exhaustion, diarrhea, and/or vomiting. Pain behind the eyeballs (postorbital) occurs on moving the head. The head, lower back, legs and joints ache. The patient feels very weak. The temperature rises rapidly, sometimes to as high as 40C or 104F, accompanied by a relatively slow heart beat (bradycardia) and abnormally low blood pressure. The lymph glands in the neck, shoulder, and groin are usually enlarged.
Two or three days after the first fever, a rash of flat or elevated (maculopapular) spots appears, particularly on the face. A second temperature rise follows. The presence of Dengue virus in the blood (viremia) can confirm the diagnosis. The patient subsequently develops immunity against this type of Dengue virus. However, reinfection with a different type of this virus is possible.
Secondary forms of Dengue Fever are Dengue Hemorrhagic Fever, and Dengue Shock Syndrome. These forms of the disorder primarily affect children between 3 and 6 years of age who have been infected a second time with dengue virus, and infants 7 to 8 months of age. These forms of the disorder are characterized by sudden fever, headache, nausea, vomiting, and abdominal pain. Coughing, throat infection and difficulty in breathing also occur. Shock may occur 2 to 6 days after the beginning of the fever, with sudden collapse, cool clammy extremities (the trunk is often warm), a weak pulse, and bluish discoloration of the skin around the mouth (cyanosis). In serious cases, a tendency to bleed excessively occurs, either as purpura or in pinpoint spots (petecchiae). The bleeding may appear in many parts of the body. Blood vessels become dilated and congested, and swelling (edema) may also occur. Gastrointestinal bleeding may lead to vomiting of blood (hematemesis) and passing of dark stools stained with blood pigment (melena).
Dengue Fever is caused by a virus that belongs to a family of viruses known as Flaviviruses. There is no vaccine, so travelers going to parts of the world where it is endemic during Dengue season (July to November) are urged to protect themselves from mosquito bites by wearing protective clothing and mosquito repellant.
Dengue Fever occurs mainly in subtropical or tropical climates including southern Asia, South America (particularly Brazil), and the Caribbean including Puerto Rico and the U.S. Virgin Islands. The virus has also been imported into the United States by tourists from these areas. It is thought that approximately 200 cases of Dengue Fever are unknowingly carried into the United States each year.
Dengue fever is diagnosed by testing a blood sample for the presence of the dengue virus or its antibodies, specifically immunoglobulin M (IgM).
The FDA approved in 2011 the first test (DENV Detect IgM Capture ELISA) to help diagnose people with signs and symptoms of dengue fever or dengue hemorrhagic fever. This test, patented by the US Centers for Disease Control and Prevention (CDC) and manufactured by InBios International, detects antibodies to dengue virus in blood samples from patients. IgM antibody response to the dengue virus infection is not detectable until 3-5 days after the onset of fever, which can produce a negative test result even though a person has dengue. During this "IgM negative window" the dengue virus is present in the bloodstream.
In 2012, the FDA approved a new diagnostic test (DENV-1-4 Real Time RT PCR Assay) developed by the CDC to detect the presence of dengue virus in people. This is the first approved assay that detects the dengue virus itself and can be performed using equipment and supplies that many public health laboratories already use to diagnose influenza. This test will permit earlier diagnosis of dengue virus infection, thus reducing the risk of death with timely care.
Complete bedrest is important. Affected individuals should take measures to avoid additional mosquito bites in order to prevent reinfection. Fluids should be given to compensate for dehydration.
Treatment for Dengue Hemorrhagic Fever depends on the individual's degree of dehydration. Affected individuals should be closely monitored to prevent shock. When skin appears bluish in color, oxygen should be given. Collapse of blood vessels and loss of fluid from the circulation (hemoconcentration) require immediate fluid replacement, preferably with a solution like Ringer's lactate. Plasma or human serum protein (albumin) should also be given if there is no response in the first hour. Fresh blood or blood platelet transfusions may control bleeding. Agitated patients may be given paraldehyde, chloral hydrate, or diazepam.
Scientists have studied the effect of human interferon on Hemorrhagic Dengue Fever. More research is needed before this drug will be available for more general use in treating Dengue Fever. Additionally, scientists are trying to develop a vaccine that may someday prevent this infectious disorder.
A pharmaceutical company known as Genelabs Technologies, Inc., is working on an RNA-binding drug program that has produced several compounds that potentially inhibit viral activity. It is hoped that this might lead to drug treatment options for RNA viruses, including yellow fever, hepatitis C, Japanese encephalitis, and Dengue fever. More research is necessary to develop and test such drugs for safety and long-term effectiveness.
Researchers at OraVax, Inc., plan to create vaccines against several forms of Dengue Fever by modifying a proven Yellow Fever vaccine. Genes from one of several types of Dengue Fever viruses will replace a gene in a Yellow Fever virus. Vaccines from the modified Yellow Fever virus will be tested for safety and efficacy against the Dengue Fever virus.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
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