Dengue fever has spread in many parts of South-East Asia since the 1950s and re-emerged in the Americas in the 1990s following deterioration in active mosquito control and spread of the vector into urban areas. Infection with dengue virus has often resulted in dengue haemorrhagic fever (DHF) in Asia, but rarely in the Americas until a severe outbreak in Cuba in 1981. Dengue haemorrhagic fever has since spread and during the epidemics in Central and South America in 1995-1997; DHF was reported in 24 countries.

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 the Central Pacific.

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

Worldwide, about 50 million cases of dengue infection occur each year, with 22,000 deaths, mostly in children. This includes 100 to 200 cases in the United States, mostly in people who have recently travelled abroad.

Many more cases likely go unreported because some healthcare providers do not recognize the disease. In the Western hemisphere, the estimated economic burden of dengue is about $2.1 billion per year.

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 (DHF) and dengue shock syndrome also have increased in many parts of the world. Globally, there are an estimated several hundred thousand cases of DHF per year.

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.

In a recent study at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), researchers discovered a key step in how the dengue virus infects a cell.

Led by Leonid V. Chernomordik, Ph.D., of  NICHD’s Membrane Biology Section, the group spent many years studying how the dengue virus is released from its own protective membrane and fuses with the target membrane in order to infect a cell.

They found that two conditions were essential for fusion: an acidic environment and a negatively charged target membrane, conditions that are present only at certain points in the infection process.

Dr. Chernomordik hopes that the new findings will allow researchers to find and test new ways of disrupting the fusion process to prevent dengue infection.

Symptoms
Classic Dengue
Symptoms of typical uncomplicated (classic) dengue usually start with fever within 4 to 7 days after you have been bitten by an infected mosquito and include:

High fever, up to 105ºF
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, and then subsides after 1 to 2 days. You may get a second rash a few days later.

Dengue Hemorrhagic Fever
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.

Dengue Shock Syndrome
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 healthcare 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 healthcare provider often can diagnose dengue by typical signs and symptoms.

Treatment
There is no specific treatment for classic dengue fever, and most people recover within 2 weeks. To help with recovery, healthcare experts recommend
Getting plenty of bed rest
Drinking lots of fluids
Taking medicine to reduce fever
The Centers for Disease Control and Prevention 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 virus infection is to take special precautions to avoid being bitten by 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 repellent 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 take 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, especially adults, may be tired and/or depressed for several weeks to months after being infected with the virus.

The more clinically severe dengue hemorrhagic fever and dengue shock syndromes can result in vascular (blood vessel) and liver damage, and can be life-threatening.

Source: National Institute of Allergy and Infectious Diseases (NIAID) & WHO Facts Sheet