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The symptoms and signs for dengue begin about three to 15 days (incubation period) after a mosquito bite transfers a virus (dengue virus serotypes 1-4) to a person previously unexposed to the viruses. Fever and painful muscle, bone, and joint aches can occur during the first few hours of symptoms when headache, chills (shivering and/or sweating), rash (may be itchy) and/or red spots or flushing, and swollen lymph nodes first appear. Pain behind or in back of the eyes is also a common symptom. Some individuals may develop a sore throat, vomiting, nausea, abdominal and/or back pain, and loss of appetite. These symptoms usually last about two to four days and then diminish, only to reappear again with a rash that covers the body and spares the face. The rash also may occur on the palms of the hands and the bottom of the feet, areas frequently spared in many viral and bacterial infections.
The symptoms may last about one to two weeks with complete recovery, in most cases, in a few weeks. However, some people can develop more severe symptoms and complications, such as hemorrhagic areas in the skin (easy bruising), gums, and the gastrointestinal tract. This condition is termed dengue hemorrhagic fever (DHF). The majority of DHF is seen in children under 15 years of age, but it can occur in adults. Another clinical variation of dengue fever is termed dengue shock syndrome (DSS); DHF usually precedes DSS. The patients eventually develop severe abdominal pain, heavy bleeding, and blood pressure drops; this syndrome, if not treated quickly, may cause death.
Dengue fever is diagnosed by a medical doctor by the relatively characteristic sequence of high fever, rash appearance, and other symptoms in a person who has a history of recent travel to dengue endemic areas and recalls mosquito bites while in the endemic area. However, if not all of the symptoms are present or the history is not complete, the caregiver is likely to run a number of tests to obtain a definitive diagnosis.
Other diseases may yield similar symptoms, for example:
• typhoid fever
• yellow fever
• scarlet fever
• Rocky Mountain spotted fever
• food poisoning
• and several others
If the patient has severe symptoms; or if the doctor does not have enough information to make a presumptive diagnosis, the patient is likely to undergo a number of other tests to definitively distinguish dengue fever from other diseases. In general, the more serious the symptoms such as easy bruising, fevers at or above 104 F, hemorrhages or shock syndrome, the more tests are likely to be done.
In general, most physicians will order a complete blood test (CBC), with a metabolic panel, along with coagulation studies in most patients with high fever and any bleeding problems. Low platelet and low white cell counts may occur with the disease. In addition, depending on the symptoms (especially headache), blood and urine cultures plus a spinal tap may be done to help differentiate between dengue fever and other diseases. A MAC-ELISA assay (an immunoglobulin M-based test) is the most widely used test for dengue fever virus. However, other tests are available; they also are based on the person's immunological response to the dengue viruses (for example, IgG-ELISA, dengue viral plaque reduction tests, and PCR tests). These tests are considered definitive for exposure to dengue virus; definitive diagnosis of dengue fever is isolation and identification (usually by immunological tests) of the dengue virus serovar from the patient.
For more information, read our full medical article on dengue fever.