Dengue fever

What is dengue fever?

This is an infection from a type of virus known as a flavivirus, which is spread by mosquitoes. The illness is found in both rural and suburban environments. Although dengue only turns up very occasionally in the UK among travellers from overseas, it is a major cause of illness worldwide, causing about 100 million episodes of feverish illness a year.

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

Symptoms

Dengue causes a variety of symptoms, including:

• High fever
• Headache
• Nausea
• 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 it’s also known as 'breakbone fever'.

Most incidences 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 or problems with abnormal clotting of the blood known as disseminated intravascular coagulation (DIC), which result in haemorrhage or bleeding from the gums, nose and various organs, along with clotting problems.

This is known as dengue haemorrhagic fever (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 (DSS) occurs. There are about half a million cases of DHF and DSS each year around the world, and if untreated about 50 per cent will die (fortunately, treatment reduces mortality to just three per cent).

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 against the virus itself. Those who are severely affected may need to be admitted to hospital for observation and supportive therapies such as intravenous fluids and oxygen.

Although it may take a number of weeks, with treatment 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.