The U.S. Centers for Disease Control and Prevention (CDC) has developed an important, new diagnostic test for dengue fever and dengue hemorrhagic fever. The new assay can detect the actual virus early in the infection when symptoms appear, while the other available test is only able to detect antibodies to the virus, which can take at least 4 days to develop after onset of symptoms. It is expected that the new test will allow for earlier diagnosis and better patient management of those with the viral infection.
Dengue fever is found throughout the world, including in the United States. It is a major public health problem in the tropics and subtropics, including Puerto Rico and the U.S. Virgin Islands, where thousands of U.S. citizens develop dengue every year, according to the CDC. Dengue is also the leading cause of fever in travelers returning to the U.S. from other parts of the Caribbean, as well as Asia and Latin America. Transmission of dengue has also occasionally occurred in the continental U.S.
Dengue is transmitted by mosquitoes infected with one of four types of dengue viruses. So far, there is neither a vaccine nor a specific drug to treat dengue. Symptoms include high fever, severe headache, severe pain behind the eyes, joint pain, muscle and bone pain, rash and mild bleeding involving the nose or gums, and easy bruising. While dengue can simply run its course in some people, it can progress to serious illness in others, resulting in severe bleeding (hemorrhage), shock, and death. Prompt diagnosis is important because supportive care and close monitoring for serious symptoms is best started early.
The new test, CDC DENV-1-4 Real Time PCR Assay, has been approved for use in the U.S. by the Food and Drug Administration (FDA) and can identify all four types of dengue virus. The equipment needed to perform the test is the same as that currently used to test for influenza and is already on-hand in many public health laboratories, facilitating implementation of the new test.
What especially sets the new test apart from the test currently in use, according to the CDC, is that it is a molecular test that detects evidence of the virus itself in the blood of infected individuals. The level of virus in the blood is usually high during the first five days of illness when symptoms are acute and when individuals typically seek medical help and get tested. The other available FDA-approved test detects antibody to dengue virus. Most people begin to develop these antibodies about four days after they become ill, but some do not have detectable levels of antibodies until after a week of illness. There may be a period of time, therefore, in which an infected person can have an antibody test result that is negative. Another reason the need for the viral test was critical was because the antibody test may report false positives for dengue in individuals who have developed antibodies in response to other viruses, such as West Nile Virus.
"The need for the new dengue diagnostic test was high," said Jorge L. Munoz-Jordan, Ph.D., chief of Molecular Diagnostics and Research at the CDC Dengue Branch. "Patients will be diagnosed sooner than before, and public health laboratories will have a clearer picture of the true number of dengue cases. Dengue is now a reportable disease in the United States, and the availability of state-of-the-art dengue diagnostics will improve patient management and the public health response to dengue."
The new test was made available to clinical and public health laboratories within the United States and internationally beginning July 2, 2012.
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Centers for Disease Control and Prevention. New CDC for Dengue Fever Approved. Available online at http://www.cdc.gov/media/releases/2012/p0620_dengue_test.html through http://www.cdc.gov. Accessed July 2012.
Centers for Disease Control and Prevention. The CDC Real Time RT-PCR Assay for Dengue Diagnosis. Available online at http://www.cdc.gov/dengue/clinicalLab/realTime.html through http://www.cdc.gov. Accessed July 2012.
MayoClinic.com. Dengue Fever. Available online at http://www.mayoclinic.com/health/dengue-fever/DS01028 through http://www.mayoclinic.com. Accessed July 2012.