Dengue Fever

Dengue is a mosquito-borne disease caused by four closely related viruses known as dengue virus (DENV) -1, -2, -3, and -4. More than 40% of the world’s population lives in dengue endemic areas with over 100 countries throughout the tropics and subtropics worldwide reporting cases. The World Health Organization (WHO) estimates that 50 million cases of dengue occur every year with 500,000 requiring hospitalization. Cases of dengue are confirmed every year among travelers returning to the United States (Mapped on this website as Dengue-Imported). However, it was not until June of 2009 that DENV infections became nationally reportable in the United States so case reporting prior to January 2010 is limited. Dengue was the leading cause of systemic febrile illness among travelers returning from the Caribbean, South America, South Central Asia, and Southeast Asia in a recent study of 17,353 ill travelers seen at GeoSentinel surveillance network clinics. In some case studies, dengue is the second most common cause of hospitalization (malaria is the most common) among travelers returning from the tropics. Locally acquired dengue (Mapped on this website as Dengue-Local) is uncommon in the continental United States. However, there have been outbreaks with locally acquired cases detected in Texas, Hawaii and Florida in the last decade. Dengue is endemic in Puerto Rico and the US Virgin Islands, and most of the US-affiliated Pacific Islands. A systematic data collection is in development for the US Virgin Islands and when the data are available, they will be mapped on this website.

Dengue is transmitted to humans principally from the bite of an infected Aedes aegypti (and less commonly Aedes albopictus) mosquito. Aedes aegypti is uniquely adapted to living in and around human habitations, where it lays eggs in artificial containers, like pet water bowls, vases, and discarded plastic trash. Female mosquitoes acquire DENV by biting viremic humans and become infective after an extrinsic incubation period of 8–12 days. The infected mosquito can then transmit DENV for the rest of its life (i.e., lifespan is approximately one month). Less common modes of DENV transmission include through exposure to DENV-infected blood, organs, or other tissues via blood transfusion, solid organ or bone marrow transplantation, and nosocomial injury (needle-stick or mucous membrane contact with spilled blood). DENV can be vertically transmitted from an infected woman to her fetus in utero or to the infant at parturition.

No specific therapeutic agents exist to treat DENV infections. Bed rest and maintenance of fluids is encouraged to prevent dehydration while the patient is febrile. A fever can be controlled with acetaminophen. Aspirin, aspirin-containing drugs, and other nonsteroidal anti-inflammatory drugs (e.g., ibuprofen) should be avoided because of their anticoagulant properties. Patients should watch for development of warning signs of dengue hemorrhagic fever as the fever declines and go to the hospital if they develop any of the following warning signs: abrupt change from fever to hypothermia, severe abdominal pain, persistent vomiting, bleeding, difficulties breathing, or altered mental status (e.g., irritability, confusion, lethargy).

There are no vaccines to prevent DENV infections and the most effective protective measure is to avoid mosquito bites. The risk of being bitten is highest at dawn and dusk. Travelers can reduce their contact with mosquitoes by wearing clothing that covers exposed skin such as long sleeve shirts and pants, applying effective insect repellent to clothing and exposed skin (the most effective repellents contain DEET (N,N-diethylmetatoluamide), and selecting accommodations with well-screened windows or air-conditioning when possible.