This is an infection from a type of virus known as a flavivirus, spread by mosquitoes in tropical and subtropical areas. The illness is found in both rural and suburban environments.

There are four different subtypes of flavivirus that cause dengue fever. Infection provides life-long immunity to the subtype causing the illness, but not to other subtypes. This means a person living in a dengue-endemic area can have more than one dengue infection during their lifetime.

Symptoms

Dengue causes a high fever, headache, nausea and weakness. It usually occurs in two phases - the initial fever, accompanied by a skin rash, usually settles after a few days only to return (usually not so severely) along with a second rash before finally disappearing again.

Dengue fever can cause severe pain in the bones, muscles and joints, and because of this is also known as 'breakbone fever'.

Most cases of dengue fever don’t lead to any permanent harm, but in a small percentage of cases there are complications. The virus can cause blood vessels to become leaky, leading to haemorrhage or bleeding from the gums, nose and various organs, along with clotting problems.

This is known as dengue haemorrhagic fever or DHF, and if untreated has a high mortality rate. In as many as one in three cases of DHF, another serious complication, known as dengue shock syndrome or DSS, occurs.

There's a much greater risk of DHF/DSS when a person has immunity to one of the other types of dengue virus as a result of previous infection.

Treatment and Recovery

Drinking plenty of fluids, taking painkillers and resting is very important since there's no specific treatment. Painkillers based on paracetamol (also known as acetaminophen) should be used as aspirin, ibuprofen and other non-steroidal anti-inflammatory painkillers can aggravate the risk of clotting problems and bleeding, and should be avoided. Those who are severely affected may need to be admitted to hospital for observation. Although it may take a number of weeks, most people recover fully without further problems.

There's no vaccination available yet, although trials are under way. So it's important when travelling to tropical regions to use mosquito repellents and to cover up with suitable clothing.

Unlike the mosquito that carries malaria, which bites in the evening or at night, the mosquito that carries dengue (Aedes aegypti) bites during the day, so it's vital to protect yourself against mosquito bites during this time.

This article was last medically reviewed by Dr Trisha Macnair in April 2009.