Dengue fever is a mosquito-borne tropical virus that infects about 20 million people each year in southeast Asia and Latin America, and can be fatal.

SYMPTOMS

Dengue symptoms usually appear a week after infection, and include a sudden high fever, headaches and severe joint and muscle pain.

The illness lasts up to ten days but complete recovery can take a month.

TREATMENT

Dengue fever is normally uncomplicated and treatment involves rest and drinking plenty of fluids.

Two of the four types of dengue fever can progress to dengue haemorrhagic fever, which causes bleeding from the nose, gums and inside the body.

RISK

Five percent of haemorrhagic cases are fatal.

Of the hundreds of thousands of haemorrhagic dengue cases reported each year, around 24,000 result in death, according to the U.N. World Health Organisation.

DENGUE HAEMORRHAGIC FEVER

Haemorrhagic dengue is most dangerous to children and people with weak immune systems, but younger children usually contract a milder form of the dengue fever.

Dengue haemorrhagic fever is treated by intensive replacement of lost fluids. Blood transfusions are sometimes necessary.

Recovery from dengue provides lifelong immunity against that type of the virus, but not against the others.

PREVENTION

No vaccine is currently available. Research is in progress to create one.

Unlike the mosquitoes that cause malaria, dengue mosquitoes are daytime feeders.

EPIDEMICS

Dengue epidemics have become larger and more frequent over the last 20 years, especially in urban areas in the tropics.

Air travel, ineffective mosquito control, poor public health and inadequate management of water, sewage and waste systems are important factors in spreading the disease.

Dengue outbreaks in Indonesia in early 2004 claimed more than 650 lives.