InRad | Innovative Research & Development

Dengue Fever

Dengue (pronounced DENgee) fever is a painful, debilitating mosquito-borne disease caused by any one of four closely related dengue viruses. These viruses are related to the viruses that cause West Nile infection and yellow fever.

Epidemiology

Dengue is a mosquito-borne infection found in tropical and sub-tropical regions around the world.
In recent years, transmission has increased predominantly in urban and semi-urban areas and has become a major international public health concern.
Severe dengue (previously known as Dengue Haemorrhagic Fever) was first recognized in the 1950s during dengue epidemics in the Philippines and Thailand. Today, severe dengue affects most Asian and Latin American countries and has become a leading cause of hospitalization and death among children in these regions.
There are four distinct, but closely related, serotypes of the virus that cause dengue (DEN-1, DEN-2, DEN-3 and DEN-4). Recovery from infection by one provides lifelong immunity against that particular serotype. However, cross-immunity to the other serotypes after recovery is only partial and temporary. Subsequent infections by other serotypes increase the risk of developing severe dengue.

Global burden of Dengue

The incidence of dengue has grown dramatically around the world in recent decades. Over 2.5 billion people – over 40% of the world’s population – are now at risk from dengue. 1.8 billion (>70%) live in Asia Pacific countries.
WHO currently estimates there may be 50-100 million dengue infections worldwide every year.
In the Western Pacific Region, 31 countries or areas have reported dengue cases in the last two decades.
Before 1970, only nine countries had experienced severe dengue epidemics. The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. South-East Asia and the Western Pacific regions are the most seriously affected.
Before 1970, only nine countries had experienced severe dengue epidemics. The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. South-East Asia and the Western Pacific regions are the most seriously affected.
Cases across the Americas, South-East Asia and Western Pacific exceeded 1.2 million in 2008 and over 2.2 million in 2010 (based on official data submitted by Member States).
Recently the number of reported cases has continued to increase.
In 2010, 1.6 million cases of dengue were reported in the Americas alone, of which 49 000 cases were severe dengue.

estimated 500 000 people with severe dengue require hospitalization each year, a large proportion of whom are children. About 2.5% of those affected die.

Transmission

Dengue fever is transmitted by the bite of an Aedes mosquito infected with a dengue virus. The mosquito becomes infected when it bites a person with dengue virus in their blood. It can’t be spread directly from one person to another person.

Symptoms of Dengue Fever

Symptoms, which usually begin four to six days after infection and last for up to 10 days, may include

Sudden, high fever
Severe headaches
Pain behind the eyes
Severe joint and muscle pain
Nausea
Vomiting
Skin rash, which appears three to four days after the onset of fever
Mild bleeding (such a nose bleed, bleeding gums, or easy bruising)

Sometimes symptoms are mild and can be mistaken for those of the flu or another viral infection. Younger children and people who have never had the infection before tend to have milder cases than older children and adults. However, serious problems can develop. These include dengue hemorrhagic fever, a rare complication characterized by high fever, damage to lymph and blood vessels, bleeding from the nose and gums, enlargement of the liver, and failure of the circulatory system. The symptoms may progress to massive bleeding, shock, and death. This is called dengue shock syndrome (DSS).
People with weakened immune systems as well as those with a second or subsequent dengue infection are believed to be at greater risk for developing dengue hemorrhagic fever.

Diagnosing Dengue Fever

Doctors can diagnose dengue infection with a blood test to check for the virus or antibodies to it. If you become sick after traveling to a tropical area, let your doctor know. This will allow your doctor to evaluate the possibility that your symptoms were caused by a dengue infection.

Treatment

There is no specific treatment for dengue fever.
For severe dengue, medical care by physicians and nurses experienced with the effects and progression of the disease can save lives – decreasing mortality rates from more than 20% to less than 1%.
Maintenance of the patient’s body fluid volume is critical to severe dengue care.

Immunization

There is no vaccine to protect against dengue. Developing a vaccine against dengue/ severe dengue has been challenging although there has been recent progress in vaccine development.
WHO provides technical advice and guidance to countries and private partners to support vaccine research and evaluation.
Several candidate vaccines are in various phases of trials.

Prevention and control

At present, the only method to control or prevent the transmission of dengue virus is to combat vector mosquitoes through
preventing mosquitoes from accessing egg-laying habitats by environmental management and modification
disposing of solid waste properly and removing artificial man-made habitats
covering, emptying and cleaning of domestic water storage containers on a weekly basis
applying appropriate insecticides to water storage containers
using personal household protection such as window screens, long-sleeved clothes, insecticidetreated materials, coils and vaporizers
improving community participation and mobilization for sustained vector control
applying insecticides as space spraying during outbreaks as one of the emergency vector control measures;
selective residual insecticide tr
eatment on indoor mosquito resting sites
active monitoring and surveillance of vectors to determine their distribution and key breeding sites for planning of effective control interventions