About Travel Risks & Dengue Fever

Dengue fever is the most common arbovirus infection worldwide, affecting up to 100 million people annually. Travelers to dengue endemic regions import 100 to 200 cases of dengue fever into the United States each year. The Centers for Disease Control and Prevention states that dengue fever incidence in tourists may be as high as 1 infection per every 1000 travelers to high risk countries.

Geography

Dengue virus is endemic to Southeast Asia, Africa, Central and South America, India, the Middle East, Caribbean and tropical Pacific islands. Dengue genotypes circulating in Southeast Asia, Central and South America, and the South Pacific may carry a higher risk of dengue hemorrhagic fever. Many countries in these regions suffer from dengue fever epidemics every three to five years.

Types

Four distinct viral serotypes (DEN-1, DEN-2, DEN-3 and DEN-4) cause dengue fever. Aedes aegypti mosquitoes transmit the dengue flavivirus. Aedes albopictus is occasionally implicated in Western hemisphere transmission, including the 2001 dengue outbreak in Hawaii.
Dengue virus causes four distinct medical conditions: nonspecific febrile illness, dengue fever (DF), dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). About 1% of dengue fever cases progress to the more severe hemorrhagic form. Dengue hemorrhagic fever has a 5% fatality rate without proper medical intervention.

Effects

Dengue virus has an incubation period of three to fourteen days from mosquito bite to onset of symptoms. Sick travelers with flu-like symptoms should consider dengue infection if their travel history includes a dengue endemic region within the previous two weeks.
Dengue virus causes fevers as high as 40-41º C (104-105.8º F), influenza-type aches, rash, headache, retro-orbital eye pain, loss of appetite, nausea and abdominal pain. Dengue fever may cause hemorrhagic bleeding of the eyes, gums, gastrointestinal tract, and other organs. Dengue fever rash generally starts on day three and spreads from the torso to extremities. Fever generally resolves after five days, but complete recovery is often slow with weeks of fatigue and depression.
Severe cases require hospitalization, oral and intravenous fluids, and possible blood transfusion. Complications usually arise on days three to five of illness. Increased vascular permeability leading to fluid accumulation in the abdomen and chest cavity characterizes dengue hemorrhagic fever (DHF). Potentially fatal circulatory decompensation occurs in dengue shock syndrome (DSS) cases.

Prevention/Solution

There are no commercially available vaccines for dengue virus. Potential vaccines are in field-testing, but will not be economical options anytime in the near future. There are no dengue specific medical treatments; care is limited to hydration and pain management. Therefore, avoiding infection should be a traveler's primary concern.
Travelers should investigate recent dengue activity in the regions they intend to visit. The Centers for Disease Control and Prevention and World Health Organization websites both offer country specific health advisories. Dengue virus transmission is highest during rainy seasons. Time your trip accordingly to minimize risk.
Travelers to dengue fever endemic regions should apply DEET mosquito products daily to clothing and exposed skin. Use repellents with more than 50% DEET concentration; apply after sunscreen. Long sleeve shirts and pants are preferable to shorts and tank tops. Aedes aegypti mosquitoes, primary carriers of dengue, feed during the morning and early evening hours. Mosquitoes may bite any time of day in air-conditioned or shady areas.
Although A. aegypti mosquitoes are day feeders, consider sleeping under a bed net treated with mosquito repellent. Tuck the net under the mattress to prevent entry. Mosquito netting is also a preferred method for protecting very young infants in carriers. Babies over two months old can use DEET mosquito repellent.
CDC mentions anecdotal outbreak evidence that travelers staying in air conditioned hotels with properly maintained grounds are at less risk of dengue fever infection than travelers staying in homes of friends and family in endemic regions.

Warning

When traveling in an area of dengue fever activity, do not take aspirin or NSAIDs (nonsteroidal anti-inflammatory drugs) like ibuprofen if you experience flu-like symptoms, rash, abdominal pain, or headache. Aspirin aggravates the hemorrhagic aspects of dengue fever. There is also a risk of Reyes Syndrome. Only use acetaminophen for pain relief.

Misconceptions

Travelers are not at high risk for severe forms of dengue fever. Prior dengue infection places a patient at higher risk of dengue hemorrhagic fever. Therefore, travelers with no prior dengue infection history are less likely to develop severe forms of the disease than natives from an endemic region.
Most people due not suffer severe illness from dengue virus infection. More than 80% of dengue cases are asymptomatic or mild.

Resources

• CDC International Traveler Health- Dengue Fever
• CDC Mosquito Bite Prevention Tips
• CDC Travel Health Information- Destination Specific