DENGUE FEVER

Dengue is a mosquito-transmitted viral disease occurring chiefly in tropical and subtropical areas of the world. Epidemic transmission is usually seasonal, during and shortly after the rainy season. There are no travel restrictions in any country with regard to dengue.

In Central and South America, dengue fever is reemerging as a threat. In November 1995, the Pan American Health Organization issued an alert that dengue and dengue hemorrhagic fever had reached epidemic proportions in the Americas. At that time, more than 200,000 cases of dengue had been reported, as well as 5,500 cases of the potentially fatal dengue hemorrhagic fever. Cases have been reported among international travelers.

Risk

Generally, there is a low risk of acquiring dengue during travel to tropical areas where dengue fever normally occurs except during periods of epidemic transmission. Dengue outbreaks have occurred with increasing frequency in recent years in most countries of the Tropics.

The risk is greatest in the Indian subcontinent, Southeast Asia, Southern China, Central and South America (except Chile, Paraguay, and Argentina), the Caribbean (except Cuba and the Cayman Islands), Mexico, and Africa. There is a somewhat lower risk for travelers to Taiwan and the Pacific Islands. The Middle East and Northern Australia have a still lower risk of Dengue transmission. New Zealand is free of dengue fever.

Since 1985, major epidemics have occurred in Mexico, Guatemala, El Salvador, Nicaragua, Columbia, Bolivia, Brazil, and the Caribbean.

Transmission

Dengue viruses are transmitted by Aedes mosquitoes, which are most active during the day, with most biting activity occurring in the morning and at twilight. Mosquitoes that transmit dengue usually are found near human dwellings and often are present indoors. Dengue is predominant in urban centers, but may be found in rural areas. It is rarely found at elevations above 4000 feet. Dengue fever may occur from 3 to 15 days after exposure to an infected mosquito, commonly within 5 to 6 days.

Symptoms

Dengue fever is characterized by sudden onset, high fever, severe headaches, intense joint and muscle pain, and fatigue. Nausea and vomiting may occur. 3-4 days after the onset of fever, a skin rash develops which may spread from the torso to the arms, legs, and face. Infection is diagnosed by a blood test that detects the presence of the virus or antibodies. The illness may last up to 10 days, but complete recovery can take 2 to 4 weeks. Dengue is commonly confused with other infectious illnesses such as influenza, measles, malaria, typhoid, and scarlet fever.

More severe forms of the disease, "dengue hemorrhagic fever" or "dengue shock syndrome" are very rare among travelers. Symptoms initially may be indistinguishable from dengue fever, but the hemorrhagic form of dengue fever is more severe and is associated with loss of appetite, vomiting, high fever, headache and abdominal pain, progressing to faintness, and generalized bleeding. Shock and circulatory failure may occur. Untreated hemorrhagic dengue results in death in up to 50 percent of cases.

If traveling in a malarious area, and develop a sudden high fever, Assume that it could be malaria, even though it may be dengue fever, or some other disease. Immediate blood tests should be done for a definitive diagnosis.

See your physician if you become sick within a month of returning from travel in a tropical area. Be prepared to give your complete travel itinerary, so that the physician can evaluate the possibility that your symptoms were caused by a dengue infection.

Prevention

There is no vaccine for dengue fever; therefore the traveler should avoid mosquito bites by using insect repellents on skin and clothing, and remaining in well screened or air conditioned areas. For skin, insect repellents should have a high (DEET) concentration. Spraying clothing with permethrin (Permanone) will increase protection. Travelers should use an insect spray containing pyrethrum indoors. Even though the mosquitoes bite during the day, the use of bednets is recommended when sleeping quarters are not screened or air conditioned.
Treatment

The symptoms of dengue can be treated with bed rest, ingestion of large amounts of fluids, and medications to reduce fever, such as acetaminophen. Aspirin should not be taken. Antibiotics are not helpful.

Diseases