Dengue fever growing hazard of the tropics

Mosquito-repellent a must for travelers

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ATLANTA (CNN) -- A stroll through the streets of some exotic port of call in the Caribbean or Asia could pose a health hazard to unsuspecting travelers. The danger is from dengue fever, an acute viral infection transmitted by mosquitoes.

Officials of the U.S. Centers for Disease Control and Prevention warn that more and more people worldwide are contracting dengue fever.

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"This is the most important viral disease transmitted by mosquitoes," Duane Gubler, a CDC health administrator, said. "The mosquitoes become infected when they feed on someone who has the virus," he added.

There is no vaccine. But travelers and residents of tropical areas can take precautions to avoid contracting this sometimes fatal illness.

Dengue is the world’s most common mosquito-borne viral disease. About 2.5 billion people in a hundred countries are at risk, said officials of the World Health Organization. Children and young adults are most vulnerable.

Like malaria, dengue is usually found in tropical regions of Latin America and Asia, the Caribbean and Africa.

However, the mosquitoes that carry the virus can be found during summer months in the southeastern United States -- specifically in Florida, Georgia, Alabama, Mississippi, Louisiana and as far west as Texas.

From 1993 through 1998, the number of dengue cases diagnosed in the United States increased, according to a CDC report. In fact, the number of cases more than doubled between 1997 and 1998, the agency said.

Officials attribute the rise to increased travel and to growing occurrences of the disease in the Caribbean and Central America.

"Just about all U.S. cases are when residents have traveled (out of the United States) and become infected," Gubler said. "In 1945, there was a dengue outbreak in Louisiana, and 35 years later, in 1980, a small outbreak in Texas, then 1986 in Texas, then in 1995, '97, '98 and '99, all in Texas."

Specialists at CDC said dengue is characterized by a sudden onset of symptoms, which include high fever, severe headaches, extreme joint and muscle pain, nausea and vomiting. A rash may appear three or four days after the fever begins.

Dengue fever may last 10 days, but complete recovery can take two to four weeks.

Some people develop dengue hemorrhagic fever (DHF), which is characterized by bleeding, in addition to the other symptoms. DHF is fatal in about 5 percent of cases, according to the CDC. An even more severe form of the disease, dengue shock syndrome (DSS), can lead to circulatory failure and shock. About 10 percent of those cases are fatal.

"Globally, there are an estimated 50 to 100 million cases of dengue fever and several hundred thousand cases of dengue hemorrhagic fever (DHF) per year," according to CDC projections.

People who suspect they have dengue fever should not take aspirin, CDC officials warned, because it can impair blood clotting. Acetaminophen is a better choice.

Doctors also need to know what countries patients may have visited recently to help them diagnose dengue. It is often mistaken for typhoid, influenza, measles, malaria or scarlet fever.

Since there is no vaccine for dengue fever, travelers are advised to avoid mosquito bites by staying in screened or air-conditioned places.

When that's not possible, visitors to tropical areas should use mosquito repellents on skin and clothing, take aerosol insecticides for indoors and use bed nets, which can be purchased in camping or military-supply stores.

CDC officials also recommend wearing long-sleeved shirts and long pants and choosing an insect repellent that contains DEET (diethylmethyltoluamide) in 30 percent to 35 percent strength for adults and 6 percent to 10 percent for children.

Visitors to tropical cities are particularly at risk because the mosquitoes that carry dengue, Aedes aegypti, thrive in urban areas. They lay their eggs in water that collects in abandoned tires, discarded bottles or even flower pots. And the adults hide indoors, in closets and bathrooms, behind curtains and under beds, the CDC report said.

The mosquitoes usually feed in the daytime, but people are at risk of being bitten at any time.

Not learning about a dengue outbreak in a country dependent on tourist dollars does not mean no outbreak exists, Gubler said. "Some countries report epidemics, and some do not."

Anyone planning to travel in tropical or subtropical areas, he said, should take precautions.

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U.S. Centers for Disease Control and Prevention
World Health Organization

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