Dengue Fever - OVERVIEW

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 that feels like bones are breaking, hence the name. 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.

Worldwide, more than 100 million cases of dengue infection occur each year. This includes 100 to 200 cases reported annually to the Centers for Disease Control and Prevention (CDC), mostly in people who have recently traveled abroad. Many more cases likely go unreported because some health care providers do not recognize the disease.

During the last part of the 20th century, many tropical regions of the world saw an increase in dengue cases. Epidemics also occurred more frequently and with more severity. In addition to typical dengue, dengue hemorrhagic fever and dengue shock syndrome also have increased in many parts of the world.

CAUSE

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

TRANSMISSION

You can 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. Two main species of mosquito, Aedes aegypti and Aedes albopictus, have been responsible for all cases of dengue transmitted in this country. Dengue is not contagious from person to person.

SYMPTOMS

Symptoms of typical uncomplicated (classic) dengue usually start with fever within 5 to 6 days after you have been bitten by an infected mosquito and include

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 your body 3 to 4 days after the fever begins. You may get a second rash later in the disease.

Symptoms of dengue hemorrhagic fever include all of the symptoms of classic dengue plus

Marked damage to blood and lymph vessels
Bleeding from the nose, gums, or under the skin, causing purplish bruises
This form of dengue disease can cause death.

Symptoms of dengue shock syndrome-the most severe form of dengue disease-include all of the symptoms of classic dengue and dengue hemorrhagic fever, plus

Fluids leaking outside of blood vessels
Massive bleeding
Shock (very low blood pressure)
This form of the disease usually occurs in children (sometimes adults) experiencing their second dengue infection. It is sometimes fatal, especially in children and young adults.

DIAGNOSIS

Your health care provider can diagnose dengue fever by doing two blood tests, 2 to 3 weeks apart. The tests can show whether a sample of your blood contains antibodies to the virus. In epidemics, a health care provider often can diagnose dengue by typical signs and symptoms.

TREATMENT

There is no specific treatment for classic dengue fever, and like most people you will 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.

For severe dengue symptoms, including shock and coma, early and aggressive emergency treatment with fluid and electrolyte replacement can be lifesaving.

PREVENTION

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 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, picaridin, or oil of lemon eucalyptus
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

Keeping unscreened windows and doors closed
Keeping window and door screens repaired
Getting rid of areas where mosquitoes breed, such as standing water in flower pots, containers, birdbaths, discarded tires, etc.
COMPLICATIONS

Most people who develop dengue fever recover completely within 2 weeks. Some, however, may go through several weeks to months of feeling tired and/or depressed.

NIAID RESEARCH

Scientists supported by the National Institute of Allergy and Infectious Diseases (NIAID) are trying various approaches to develop vaccines against dengue. 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 NIAID-funded investigators are trying to develop dengue virus vaccines using recombinant proteins (with or without adjuvants), viral vectors, and DNA.

Several projects are currently ongoing to identify the host and viral factors that determine the virulence and transmissibility of different dengue virus strains.

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

Although dengue virus has 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.