Dengue fever is a viral infection transmitted to humans by mosquitoes that live in tropical and subtropical climates and carry the virus. Blood testing detects the dengue virus or antibodies produced in response to dengue infection.
If a person develops a fever within two weeks following travel to an area where dengue fever is present, it may be prudent to test for dengue fever. According to the Centers for Disease Control and Prevention (CDC), dengue infections have been reported in more than 100 countries from parts of Africa, the Americas, the Caribbean, the Eastern Mediterranean, Southeast Asia, and the Western Pacific. It is a fast emerging infectious disease, according to the World Health Organization (WHO), with an increasing number of cases and countries affected throughout the world. Approximately 50 to 100 million cases occur annually worldwide.
In the U.S., the majority of dengue cases occur in travelers returning from areas where dengue is endemic. Most dengue cases in U.S. citizens occur in those inhabitants of Puerto Rico, the U.S. Virgin Islands, Samoa and Guam. Outbreaks where a large number of cases occur in a defined area are rare in the U.S. In recent years, there have been small outbreaks in Texas and Hawaii and a few cases diagnosed in southern Florida.
Many individuals will develop no symptoms at all, or have only a mild illness when exposed to one of the four serotypes of the dengue virus. For those who do develop symptoms, prognosis is still very good for full recovery within a few weeks. The most common initial symptoms are a sudden high fever (104?F or 40?C) and flu-like symptoms that appear roughly 4 to 7 days after being bitten by an infected mosquito (this is called the incubation period and can range from 3 to 14 days). Additional signs and symptoms may include severe headache, especially behind the eyes, muscle and joint pain, skin rash, nausea, vomiting, and swollen glands.
Some people who develop a fever will recover on their own with no lasting ill effects while others may progress to severe dengue fever (sometimes called Dengue Hemorrhagic Fever). If the disease progresses to this form, a new wave of symptoms will appear 3 to 7 days after initial symptoms and as the fever recedes. These may include nose bleeds, vomiting blood, passing blood in the stool, difficulty breathing and cold clammy skin, especially in the extremities. During the second phase, the virus may attack blood vessels (the vascular system), causing capillaries to leak fluid into the space around the lungs (pleural effusion) or into the abdominal cavity (ascites). Currently, there is no explanation as to why dengue fever resolves itself harmlessly in some people while progressing to the severe form in others.
The loss of blood and fluid during the second phase, if untreated, can sometimes develop into a rare condition known as Dengue Shock Syndrome and can be fatal. In order to avoid that complication, a doctor may hospitalize a patient with dengue fever so that falling blood pressure and dehydration caused by the loss of blood and fluids can be managed while the disease runs its course ? generally a period of one to two weeks. During the following week of recovery, a person may develop a second rash that lasts a week or more.
Dengue fever is usually diagnosed via some combination of blood tests because the body's immune response to the virus is dynamic and complex. Laboratory tests may include:
Molecular tests for dengue virus (PCR)?detect the presence of the virus itself; these tests can diagnose dengue fever up to 5 days after the onset of symptoms.
Antibody tests, IgM and IgG?detect antibodies produced by the immune system when a person has been exposed to the virus; these tests are most effective when performed at least 7-10 days after exposure.
Complete blood count (CBC)?to look for low platelet count typical of the later stages of the illness and to detect the decrease in hemoglobin, hematocrit, and red blood cell (RBC) count (evidence of anemia) that would occur with blood loss associated with severe dengue fever.
Basic metabolic panel (BMP) ? to monitor kidney function and look for evidence of dehydration that can occur with severe illness.
To diagnose dengue fever, particularly if you are experiencing fever after travel to a tropical or subtropical destination. When you develop a high fever within 2 weeks of travel to an area where dengue fever is endemic or an outbreak is occurring.
Testing may be ordered when individuals have signs and symptoms associated with dengue following travel to tropical locations where the virus is present. Some of the main signs and symptoms include:
Sudden high fever (104?F or 40?C)
Severe headache or pain behind the eyes
Joint, muscle and/or bone pain
Gum and nose bleeds
Low white blood cell count
Testing is usually ordered within one to two weeks of the onset of symptoms to detect an acute infection. If antibody testing is performed, an additional blood sample may be collected after two weeks of symptoms to determine if the antibody level is rising.