Dengue Fever 101

July 29, 2010 — -- Dengue (pronounced DEN-ghee) fever is a tropical disease spread by mosquitoes. It is caused by any one of four closely related dengue viruses -- DENV 1, DENV 2, DENV 3 or DENV 4 -- carried most often by the Aedes aegypti mosquito, and less frequently, by Aedes albopictus.

The most common vector-borne viral disease in the world, it causes an estimated 50-100 million infections and 25,000 deaths each year.

Generally most prevalent in tropical and subtropical areas, dengue made a return to Key West, Fla., in 2009 after being absent since 1934.

There were 27 known cases there last year and 18 so far this year. Some carriers never feel ill, but many sufferers report excruciating bone pain, leading some to call dengue "break-bone fever." Complications can be fatal.

Why is dengue fever an issue now in the United States?

No one can say for sure why it turned up South Florida, but a May report from the U.S. Centers for Disease Control and Prevention in Atlanta suggests some possibilities:

Dengue might have been present in the community earlier, but is only being detected now.

The conditions for dengue transmission long have been present in South Florida. Epidemiologists say dengue could have reappeared in Florida when an infected international visitor passed the virus to local mosquitoes, or a mosquito carrying dengue hopped a ride on a cruise ship or airplane. Key West has lots of Aedes aegypti, a mosquito that is the most effective dengue carrier.

The large numbers of domestic visitors also might increase the risk for spread in other parts of the United States.

It's misleading to think there's been no dengue fever in the United States until now. In fact, in the last five years, there have been dengue outbreaks in both Florida and Texas, according to the American Society of Tropical Medicine and Hygiene.

The disease disappeared from 1946-1980, when there were no reported cases acquired in the continental United States. Then, beginning in the 1980s, dengue fever re-emerged as a widespread tropical infection throughout Central America and the Caribbean, especially in Cuba, the Dominican Republic and Puerto Rico.

Since 1980, there have been seven localized outbreaks along the Texas-Mexico border, including one in the small border town of Brownsville, Texas, in 2005.

Where do health officials expect dengue to hit next?

The American Society of Tropical Medicine and Hygiene says that based on recent outbreaks, dengue could become a health threat in major Gulf Coast cities such as Corpus Christi, Texas; Houston; New Orleans; Biloxi, Miss.; Mobile, Ala.; Pensacola, Fla., and Tampa, Fla., as well as in less populated areas.

Right now, CDC officials are keeping a close eye on Puerto Rico, where suspected dengue cases are being recorded at a level unseen since a major epidemic in 1998. There are major similarities between worldwide climate patterns in 2009-10 and those in 1997-98, when there also was a strong El Nino climate phenomenon that brought warmer weather to Puerto Rico. Dengue viruses reproduce more rapidly in warm weather, according to Robert S. Hope of Yale University.

What are the signs and symptoms of dengue?

The incubation period for dengue fever is typically 4 to 7 days, but can be 3 to 14 days. The main symptoms are a high fever and at least two of the following:

Severe headache

Severe pain behind the eyes

Joint pain

Muscle and/or bone pain

Rash

Mild bleeding: nose bleed, bleeding gums, easy bruising or tiny broken blood vessels called petechiae

Low white cell count

What are the complications of dengue?

People who have been infected with one strain can be infected with another. Sequential infections put them at increased risk for dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), which can be fatal.

DHF is a very dangerous form of dengue infection. It can be fatal if unrecognized and not properly treated. DHF is caused by infection with the same viruses that cause dengue fever. It can cause internal bleeding and a drop in blood pressure, followed by shock and sometimes death. Fluid in the blood can leak through the skin and into the spaces around the lungs and belly. With good medical management, mortality due to DHF can be less than 1 percent.

Dengue shock syndrome (DSS) is dengue hemorrhagic fever with signs of circulatory failure. The fatality rate can be as low as 0.2 percent with early treatment, but once shock has set in, the mortality rate can be 12 percent to 44 percent.

Are there any treatments for dengue?

Right now, there are no specific medications to treat its symptoms and no vaccine. However, there are several vaccines in development:

Dr. Anna Durbin, an associate professor in international health at the Johns Hopkins Bloomberg School of Public Health, is conducting clinical trials in Baltimore -- and later this summer in Brazil -- with an experimental dengue vaccine created by the National Institutes of Health. She is also part of the Pediatric Dengue Vaccine Initiative (PDVI), an international consortium of scientists, drug manufacturers and public health institutions.

The pharmaceutical company Sanofi Aventis, which has been testing its ChimeriVax dengue vaccine in tropical countries, predicts it will have a dengue vaccine on the market by 2015.

Another potential dengue vaccine is being jointly developed by GlaxoSmithKline and several U.S. agencies, including the CDC and Armed Forces Research Institute of Medical Sciences.

What can I do if I get dengue?

You can use pain relievers containing acetaminophen (Tylenol), but should avoid aspirin, aspirin-containing medications or those containing ibuprofen (Advil, Motrin), or naproxen (Aleve, Naprosyn). Rest, drink plenty of fluids to prevent dehydration, avoid mosquito bites while you have a fever and consult a physician.

How can I reduce my risk of dengue infection?

Prevention is key and that starts with avoiding mosquito bites if you live in or are traveling through an area where there is dengue.

The best way to reduce mosquito bites is to eliminate where mosquitoes lay their eggs, such as containers that hold water in and around the home. Don't keep water outdoors in pet bowls. Cover water storage barrels. Beware of standing water inside your home in vases holding fresh flowers; clean these at least once weekly.

Adult mosquitoes like to bite inside as well as around homes during the day or at night when lights are on. Use insect repellent day and night. When possible, wear long sleeves and pants. Check that window and door screens are secure and repair any holes. If possible, use air conditioning.

If someone in your home has dengue, take extra steps to prevent mosquitoes from biting the patient and then spreading dengue by biting others. Sleep under mosquito netting.