Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.See all posts »
Test for Dengue Fever
Asian tiger mosquito, Aedes albopictsDengue fever is a viral (flavivrus) disease transmitted by Aedes albopictus and female A. aegypti mosquitoes. It is estimated that 50 to 100 million people in more than 100 countries are infected each year with dengue viruses.
There are four different types of dengue virus, and there is no cross-immunity, so a person may be stricken with dengue fever four times in his life. The most active feeding times for dengue vector mosquitoes is for a few hours after daybreak and in the afternoon for a few hours just after dark (dusk).
As opposed to the night-feeding mosquitoes that transmit malaria, these species tend to be “urban,” may also feed during daylight hours (also indoors, in the shade, and during overcast weather), and are known to bite below the waist. Dengue fever is seen chiefly in the Caribbean and South America, as well as other tropical and semitropical areas, such as Southeast Asia, Africa, and Mexico. In the United States, cases have been noted in Texas, Hawaii and Florida. The larvae flourish in artificial water containers (e.g., vases, tires), often in a domestic environment.
The incubation period following a mosquito bite is two to eight days. The disease is self-limited (five to seven days) and characterized in older children and adults by a sudden onset of symptoms, including:
- severe headache
- sore throat
- high fever (greater than 39o C or 102.2 o F)
- muscle aches
- sore throat
- reddened eyes
- enlarged lymph nodes
- bone and joint pain (“breakbone fever”)
- a fine, red, itchy skin rash that typically appears simultaneously with the fever on the proximal arms, legs, and trunk (it spares the face, palms, and soles)
It may then spread to the face, and farther out on the arms and legs, becoming slightly darker and more solid. Although the fever usually remits spontaneously, an occasional victim will relapse. Some victims have a cycle of a few days of fever, then one to three days without fever, then fever again.
It is not uncommon to suffer central nervous system manifestations, including:
- severe altered mental status
Children under one year of age appear to be particularly vulnerable to especially severe forms of dengue virus infection (which also affect individuals of all ages) associated with severe bleeding problems, or dengue hemorrhagic fever, which includes:
- bleeding gums
- severe abdominal pain
- bloody vomit
- darkened stool
Another concern is circulatory problems that can lead to extremely low blood pressure. When this occurs, the victim may develop a diffuse, dark purple blotchy rash caused by bleeding into the skin.
According to the Centers for Disease Control (CDC), the principal symptoms of dengue are high fever and at least two of the following symptoms:
- severe headache
- severe pain behind the eyes
- joint pain
- muscle and/or bone pain
- mild bleeding (from the nose or gums,within the skin – bruising or red spots)
- low white blood cell count
Treatment is supportive and based upon symptoms. Fever should be treated with acetaminophen, and not with aspirin, ibuprofen or naproxen. One should get plenty of rest and stay well hydrated. There is no vaccine available against dengue fever. Insect repellents (particularly those containing DEET) are critical for prevention.
On April 8, 2011, the Food and Drug Administration (FDA) announced that it was allowing marketing of the first test to help diagnose people with signs and symptoms of dengue fever or dengue hemorrhagic fever. The DENV Detect IgM Capture ELISA test detects antibodies to dengue virus in blood samples from patients who have signs and symptoms of dengue. The test will be available for use in clinical laboratories. It is manufactured by Inbios, Inc. of Seattle, Washington.
The test is intended for use in people who show signs or symptoms of dengue, not for people who are well. The test will not turn “positive” until three to five days after the onset of fever, even though the dengue virus may already be in the bloodstream. The test may cross-react with other closely-related viruses, such as the one that causes West Nile disease. According to the FDA, in most testing situations in the U.S. in which a dengue test would be ordered by a health care provider, if the test turns out positive, it is likely because of an infection with dengue virus.
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