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Dengue fever

Dengue fever is a viral illness transmitted by Aedes mosquitoes. It occurs in many tropical countries and can affect people from the UK who are travelling abroad.

  • About dengue fever
  • Causes
  • Symptoms
  • Complications
  • Diagnosis
  • Treatment
  • Prevention
  • Further information
  • Sources
  • Related topics

About dengue fever

Dengue fever is a severe, flu-like illness caused by a virus and spread by mosquitoes. It is found in tropical countries around the world including South East Asia, India, the Caribbean, South and Central America, and Africa. While dengue fever is not found naturally in the UK, you may be at risk of catching it if you travel to one of these areas and do not protect yourself against mosquito bites. The majority of cases of dengue fever reported in the UK are associated with travel to South East Asia and India.

The number of people from the UK catching dengue fever has risen over the past few years. This is due to more people travelling to affected areas for holidays and to visit friends and relatives, as well as the virus becoming more widespread in the affected areas.

Causes

Dengue fever is caused by a type of virus called a flavivirus, which is transmitted by infected Aedes mosquitoes. A mosquito can acquire the flavivirus by biting an infected person, and is then able to transmit the virus to another person. The mosquito remains infectious for the rest of its life.

There are four forms (serotypes) of the virus that can cause the disease. If you have been infected with one form of the virus, you will be immune against being infected with that type again for the rest of your life. However, you will still be at risk of infection with the other three forms of the virus. Furthermore, if you are infected a second time, you will be at greater risk of more serious disease and a serious complication, called dengue haemorrhagic fever.

Symptoms

Dengue fever can present in a number of different ways. It takes about three to 14 days from when you become infected with the virus for symptoms to appear. This is called the incubation period. Some people who get dengue fever don't have any symptoms at all. Young children often have a fever with a rash, but other symptoms are minor.

Older children and adults may also just have mild symptoms, however they are more likely to experience classic dengue. Classic dengue is characterized by an abrupt onset of a high fever that may last up to five days, and can sometimes have two phases (known as biphasic or saddleback). You may also have the following symptoms:

  • severe headache
  • muscle and joint pain - dengue fever is sometimes referred to as break-bone fever due to the severe muscle and joint pain it can cause
  • pain behind your eyes, especially when you move your eyes
  • flushing of your face
  • sickness and vomiting
  • a bumpy, red rash (called a maculopapular rash) which starts on your chest, back or stomach and spreads to your limbs and face

These symptoms can also be caused by problems other than dengue fever. You should visit your GP for advice.

Complications

Dengue fever can sometimes develop into a more serious illness, called dengue haemorrhagic fever. This is rare in travellers, and mostly occurs in children living in countries where the virus is common. It is thought that it may develop if you have been infected before with a different type of flavivirus.

If you have dengue haemorrhagic fever, you may have bleeding under your skin, from your gums and your nose, and you may vomit blood or pass blood in your stools. These symptoms of increased bleeding (haemorrhage) can also sometimes occur in normal dengue fever. If you have any of these symptoms, you should see your GP.

In severe cases of dengue haemorrhagic fever, the condition can suddenly worsen and lead to shock (dengue shock syndrome), which can be fatal without proper treatment.

Early warning signs for dengue shock syndrome include severe abdominal pain, persistent vomiting, a sudden, marked drop in temperature and mood changes, such as irritability.

Diagnosis

You should visit your GP if you feel ill after returning from an area affected by dengue (eg South East Asia). Your GP will ask about your symptoms and examine you. You should inform your doctor that you have recently travelled abroad.

If your doctor suspects you have dengue fever, you might be asked to have some blood tests. This is to see whether you have certain antibodies for dengue fever in your blood, and will confirm whether you have the infection. Blood tests can also determine if you have developed dengue haemorrhagic fever.

Treatment

Mild symptoms

There isn't a specific treatment that can be given for dengue fever. Instead, you will probably be advised to rest, and be given supportive care - such as paracetamol, to relieve your pain and reduce your fever. You should not take aspirin or ibuprofen, as this can aggravate any bleeding symptoms you may have. Your doctor will probably also advise you to drink lots of fluids, or take oral rehydration therapy (a solution containing salts and other substances) to make sure you don't become dehydrated.

Symptoms of dengue fever normally last for about a week. However, it can take a bit longer to get completely back to normal: you may experience fatigue, depression, a loss of appetite and a general feeling of being unwell for several weeks after your fever has gone.

Severe symptoms and dengue haemorrhagic fever

If you are severely dehydrated, have severe symptoms of dengue haemorrhagic fever or your symptoms suddenly get worse, you will need to be admitted to hospital. The main treatment for dengue haemorrhagic fever is to give intravenous fluids to maintain your fluid volume. You will be given the fluids via a drip in your arm. The majority of patients make a full recovery if they receive appropriate treatment.

Prevention

The only way to prevent catching dengue fever at present is to protect yourself from getting mosquito bites. Scientists are trying to develop vaccines against the four different types of the virus, but these are not yet available.

General advice for avoiding mosquito bites normally includes sleeping under a mosquito net and wearing loose-fitting long trousers and long-sleeved tops in the evening. However, these measures aren't very effective against dengue, as the Aedes mosquito that transmits the infection normally bites during the day.

The following measures should also be taken to avoid getting bitten by mosquitoes during the day.

  • Wear light-coloured, protective clothing, covering as much of the body as possible.
  • Use an insect repellent on exposed skin and clothing, especially around dawn and dusk when the Aedes mosquito is most active. Repellents containing a chemical known as DEET (N, N-diethylmetatoluamide) are thought to be most effective.
  • Use insecticide sprays to kill mosquitoes.
  • Avoid areas where the mosquitoes breed (normally in standing water in domestic containers, around urban areas). You can also remove such sources of water or cover them to prevent access by mosquitoes.

Further information

Foreign and Commonwealth Office

National Travel Health Network and Centre

Health Protection Agency

Sources

  • Dengue fever information sheet. National travel health network and centre. www.nathnac.org, accessed 3 March 2008
  • Foreign travel associated illness, England, Wales and Northern Ireland, 2007 report. Health Protection Agency, August 2007
  • Dengue and dengue haemorrhagic fever, factsheet no 117. World Health Organisation. www.who.int, accessed 3 March 2008
  • Gibbons RV and Vaughn DW, Dengue: an escalating problem. BMJ 2002. 324:1563-1566
  • Dengue and dengue hemorrhagic fever: information for health care practitioners. Centers for Disease Control and Prevention. www.cdc.gov, accessed 3 March 2008
  • Ligon BL. Dengue fever and dengue hemorrhagic fever: a review of the history, transmission, treatment and prevention. Seminars in pediatric infectious diseases, 2005. 16(1):60-65
  • Insect bite avoidance. National travel health network and centre. www.nathnac.org, accessed 3 March 2008

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