Denge

Clinical Manifestation

Key Facts                                                                  Dengue is a mosquito-borne infection that causes a severe flu-like illness, and sometimes a potentially lethal complication called dengue haemorrhagic fever                                 Global incidence of dengue has grown dramatically in recent decades.

Dengue is a mosquito-borne infection that in recent decades has become a major international public health concern. Dengue is found in tropical and sub-tropical regions around the world, predominantly in urban and semi-urban areas.

Dengue haemorrhagic fever (DHF), a potentially lethal complication, was first recognized in the 1950s during dengue epidemics in the Philippines and Thailand. Today DHF affects most Asian countries and has become a leading cause of hospitalization and death among children in the region.

There are four distinct, but closely related, viruses that cause dengue. Recovery from infection by one provides lifelong immunity against that virus but confers only partial and transient protection against subsequent infection by the other three viruses. There is good evidence that sequential infection increases the risk of developing DHF.

Transmission

WHO/TDR/Stammers

Dengue viruses are transmitted to humans through the bites of infective female Aedes mosquitoes. Mosquitoes generally acquire the virus while feeding on the blood of an infected person. After virus incubation for eight to 10 days, an infected mosquito is capable, during probing and blood feeding, of transmitting the virus for the rest of its life. Infected female mosquitoes may also transmit the virus to their offspring by transovarial (via the eggs) transmission, but the role of this in sustaining transmission of the virus to humans has not yet been defined.

Infected humans are the main carriers and multipliers of the virus, serving as a source of the virus for uninfected mosquitoes. The virus circulates in the blood of infected humans for two to seven days, at approximately the same time that they have a fever; Aedes mosquitoes may acquire the virus when they feed on an individual during this period. Some studies have shown that monkeys in some parts of the world play a similar role in transmission

Immunization

There is no vaccine to protect against dengue. Although progress is underway, developing a vaccine against the disease - in either its mild or severe form - is challenging.

• With four closely related viruses that can cause the disease, the vaccine must immunize against all four types to be effective.
• There is limited understanding of how the disease typically behaves and how the virus interacts with the immune system.
• There is a lack of laboratory animal models available to test immune responses to potential vaccines.

Despite these challenges, two vaccine candidates have advanced to evaluation in human subjects in countries with endemic disease, and several potential vaccines are in earlier stages of development. WHO provides technical advice and guidance to countries and private partners to support vaccine research and evaluation.

It is recommended that you get the vaccine against this disease in case you are planning to visit any of the following countries:

Antigua and Barbuda	Argentina	Barbados	Belize
Bolivia	Brazil	Cambodia	Chile
China	Colombia	Cuba	Dominica
Dominican Republic	Ecuador	Fiji	Grenada
Guatemala	Guyana	Haiti	India
Indonesia	Jamaica	Laos	Malasya
Mexico	Pakistan	Palau	Papau New Guinea
Paraguay	Peru	Pilippines	Puerto Rico
Saint Kitts and Nevis	Saint Vincent and the Grenadines	Singapore	Solomon Islands
Suriname	Thailand	Trinidad and Tobago	Uruguay
Vanuatu	Venezuela	Vietnam