Dengue Fever: NIAID

WHAT IS DENGUE FEVER?

Dengue fever is an infectious disease carried by mosquitoes and caused by any of four related dengue viruses. This disease used to be called break-bone fever because it sometimes causes severe joint and muscle pain. Health experts have known about dengue fever for more than 200 years.

Dengue fever is found mostly during and shortly after the rainy season in tropical and subtropical areas of

• Africa
• Southeast Asia and China
• India
• Middle East
• Caribbean and Central and South America
• Australia and the South and Central Pacific

An epidemic in Hawaii in 2001 is a reminder that many states in the United States are susceptible to dengue epidemics because they harbor the particular types of mosquitoes that transmit it.

The World Health Organization estimates 50 million cases of dengue infection occur each year. This includes 100 to 200 cases reported annually to the U.S. Centers for Disease Control and Prevention (CDC), mostly in people who have recently traveled abroad. From 1977 to 1994, U.S. health care workers reported to CDC 2,248 cases of dengue that had been imported into this country. Many more cases probably go unreported because some doctors do not recognize the disease.

During the last part of the 20^th century, cases of dengue began to increase in many tropical regions of the world. Epidemics also began to occur more frequently, and to be more severe. In addition to typical dengue, a severe influenza-like disease-dengue hemorrhagic fever-also has been increasing in many parts of the world.

HOW IS DENGUE FEVER TRANSMITTED?

People get dengue virus infections from the bite of an infected Aedes mosquito. Mosquitoes become infected when they bite infected humans, and later transmit infection to other people they bite. The two main species of mosquito, Aedes aegypti and Aedes albopictus, have been responsible for all cases of dengue transmitted in this country.

WHAT KIND OF VIRUS CAUSES DENGUE FEVER?

Dengue fever can be caused by any one of four types of dengue virus: DEN-1, DEN-2, DEN-3, and DEN-4. A person can be infected by at least two, if not all four types at different times during a life span, but only once by the same type.

WHAT ARE THE SYMPTOMS OF DENGUE FEVER?Symptoms of typical uncomplicated dengue usually start with fever within 5 to 6 days after a person has been bitten by an infected mosquito.

• High fever, up to 105 degrees Fahrenheit
• Severe headache
• Retro-orbital (behind the eye) pain
• Severe joint and muscle pain
• Nausea and vomiting
• Rash

The rash may appear over most of the body 3 to 4 days after the fever begins. A second rash may appear later in the disease.

Interestingly, most children infected with dengue virus never develop typical symptoms.

HOW IS DENGUE FEVER DIAGNOSED?

A doctor or other health care worker can diagnose dengue fever by doing a blood test. The test can show whether the blood sample contains dengue virus or antibodies to the virus. In epidemics, dengue is often clinically diagnosed by typical signs and symptoms.

HOW IS DENGUE FEVER TREATED?

There is no specific treatment for dengue fever, and most people recover completely within 2 weeks. To help with recovery, health care experts recommend

• Getting plenty of bed rest.
• Drinking lots of fluids.
• Taking medicine to reduce fever.

CDC advises people with dengue fever not to take aspirin. Acetaminophen or other over-the-counter pain-reducing medicines are safe for most people.

HOW CAN DENGUE FEVER BE PREVENTED?

The best way to prevent dengue fever is to take special precautions to avoid contact with mosquitoes. Several dengue vaccines are being developed, but none is likely to be licensed by the U.S. Food and Drug Administration in the next few years.

When outdoors in an area where dengue fever has been found,

• Use a mosquito repellant containing DEET.
• Dress in protective clothing—long-sleeved shirts, long pants, socks, and shoes.

Because Aedes mosquitoes usually bite during the day, be sure to use precautions especially during early morning hours before daybreak and in the late afternoon before dark.

Other precautions include

• Keep unscreened windows and doors closed.
• Keep window and door screens repaired.
• Get rid of areas where mosquitoes breed, such as standing water in flower pots or discarded tires.

CAN DENGUE FEVER LEAD TO OTHER HEALTH PROBLEMS?

Most people who develop dengue fever recover completely within two weeks. Some, however, may go through several weeks of feeling tired and/or depressed.

Others develop severe bleeding problems. This complication, dengue hemorrhagic fever, is a very serious illness which can lead to shock (very low blood pressure) and is sometimes fatal, especially in children and young adults.

NIAID RESEARCH

Scientists supported by the National Institute of Allergy and Infectious Diseases (NIAID) are trying to develop a vaccine against dengue by modifying an existing vaccine for yellow fever. Researchers in NIAID laboratories in Bethesda, Maryland, are using weakened and harmless versions of dengue viruses as potential vaccine candidates against dengue and related viruses.

Other researchers supported by NIAID are investigating ways to prevent dengue viruses from reproducing inside mosquitoes.

Because dengue virus has only recently emerged as a growing global threat, scientists know little about how the virus infects cells and causes disease. New research is beginning to shed light on how the virus interacts with humans — how it damages cells and how the human immune system responds to dengue virus invasion.