Dengue is a common viral infection spread by mosquitoes. It is widespread in tropical and sub-tropical regions.
Symptoms of dengue include:
- a high temperature (fever) that can reach as high as 41C (105.8F)
- pain behind the eyes
- bone, muscle and joint pain
You should see your GP if you develop a fever or flu-like symptoms within two weeks of returning from an area where the dengue virus is common. Alternatively, you can call NHS 111 for advice.
Read more about the symptoms of dengue.
What causes dengue?
Dengue is spread by infected mosquitoes – most commonly the Aedes aegypti mosquito.
An infected human is bitten by a mosquito, the infected mosquito then bites another human, and the cycle continues.
The condition is widespread in areas of the world with a high mosquito population and has been spread by the trade in worn car tyres, which collect water where mosquitoes breed. Typically, dengue occurs in areas that have a combination of:
- a warm and humid climate
- overcrowding and major urban centres
The mosquitoes that spread dengue are rare in England, and cases that develop in the UK occur in travellers who picked up the infection overseas.
Dengue cannot be spread from one person to another.
Read more about the causes of dengue
If you have travelled to a country with dengue and develop symptoms after you return to the UK, go straight to your nearest healthcare professional (either a GP or hospital). If you go to a local doctor familiar with dengue, they will probably be able to diagnose the condition just by looking at you and asking about your symptoms. Remember to tell them you have been travelling, as other tropical viruses may cause similar symptoms. Your medical and travel history will be taken and you will be asked about your exposure to mosquitoes. You will also be given a blood test to see what effect the infection has had on your blood, and to confirm whether the dengue virus is present in your bloodstream.
If you have travelled to a country with dengue and develop symptoms after you return to the UK, go straight to your nearest healthcare professional (either a GP or hospital).
If you go to a local doctor familiar with dengue, they will probably be able to diagnose the condition just by looking at you and asking about your symptoms. Remember to tell them you have been travelling, as other tropical viruses may cause similar symptoms.
Your medical and travel history will be taken and you will be asked about your exposure to mosquitoes.
You will also be given a blood test to see what effect the infection has had on your blood, and to confirm whether the dengue virus is present in your bloodstream.
Dengue usually clears up by itself within around one to two weeks.
There are no specific medications to treat the disease, but symptoms can be managed by taking paracetamol, drinking plenty of fluids and resting.
Read more about the treatment of dengue.
A very small number of people with dengue go on to develop a more serious form of the disease known as “severe dengue”. Severe dengue is a potentially fatal complication of dengue that can lead to shock (a sudden drop in blood pressure), bleeding and organ damage.
People who get this complication will need to be admitted to hospital as a precaution.
Read more about the complications of dengue.
There is currently no vaccine for dengue fever, so the best way to prevent catching the infection is to take common sense precautions when travelling in high-risk areas, such as:
- wear protective clothing
- using a mosquito repellent throughout the day
Read more about reducing your risk of getting dengue.
Who is affected
Anyone can develop dengue, and it is estimated that 100 million cases of dengue occur each year worldwide.
There can be sudden outbreaks of cases (epidemics) where thousands of people can become infected in a short space of time.
In 2013, there were 541 reported cases in England, Wales and Northern Ireland. Most of these cases were in people returning from destinations such as India, Thailand and Barbados.
Symptoms of dengue
Symptoms of dengue usually develop 4-10 days after being exposed to the dengue virus.
Symptoms of dengue in adults include a fever (high temperature) of 40C (104F) and at least two of the following symptoms:
- severe headache
- pain behind the eyes
- muscle and joint pain
- nausea or vomiting
- swollen glands
Young children may have a rash, along with a fever.
Symptoms usually pass within a week, but it can take several more weeks to make a full recovery. It’s common to feel very tired when recovering from this type of infection.
When to seek medical advice
You should see your GP if you develop a fever or flu-like symptoms within two weeks of returning from an area where the dengue virus is common:
- South East Asia
- the Caribbean
- the Indian Subcontinent
- South and Central America
- the Pacific Islands
Alternatively, you can call NHS 111 for advice.
There is little your GP can do to speed up the infection’s course, but it’s important to get your condition diagnosed in case there’s a more serious cause of your symptoms.
Causes of dengue
Dengue is spread by infected mosquitoes, usually the Aedes aegypti and albopictus varieties.
Transmission of the dengue virus happens in a cycle. An infected human is bitten by a mosquito, the infected mosquito then bites another human, and the cycle continues.
Aedes aegypti and albopictus mosquitoes
These mosquitoes bite during the day, most often early in the morning, or in the evening before dusk.
These types of mosquitoes are often found in pools of stagnant water near humans – for example, containers near building sites or other discarded human waste. Old car tyres are a particular problem, because water collects inside them, allowing Aedes albopictus mosquitoes to breed.
Rates of dengue are often high in major cities in the developing world that have poor sanitation.
Your risk of catching dengue increases if you spend time living or working in larger towns and cities in the developing world. For example, many aid workers contract dengue at least once in their career.
Areas of the world where the dengue virus is common include:
- South East Asia
- the Caribbean
- the Indian Subcontinent
- South and Central America
- the Pacific Islands
Read more about preventing dengue.
There are four different strains of the dengue virus: DEN 1, DEN 2, DEN 3 and DEN 4.
Once you are infected by one of the strains, you should develop life-long immunity against that strain, but further infections with a different strain are possible.
If you’re infected by a different strain, you have a slightly increased chance of developing more serious complications, such as severe dengue (read more about the complications of dengue fever). This increased risk disappears if you are infected with a third or fourth strain.
Growing populations and an increase in global travel have resulted in the virus spreading.
There is currently no cure for dengue, so treatment involves trying to relieve your symptoms while the infection runs its course.
It is recommended that you:
- use paracetamol to relieve symptoms of pain and fever – the use of aspirin or ibuprofen is not recommended, as they can trigger internal bleeding in people with dengue
- drink plenty of fluids to prevent dehydration – if you are currently travelling, make sure you only drink bottled water from properly sealed bottles and not tap water
- get plenty of bed rest
If you do not notice any improvement in your symptoms after three to five days, you should seek further medical advice.
Getting back to normal
You will feel tired and unwell for a while. Most people recover within two weeks, although it can sometimes take up to six weeks for you to get completely better.
If you are worried about any aspect of your treatment or diagnosis when abroad, see your GP when you get home. Make sure you tell them where you have been, what your symptoms were and what treatment you received.
Complications of dengue
In rare cases, a person with dengue goes on to develop a more serious and potentially life-threatening form of the condition, known as severe dengue.
People who have had dengue before are thought to be the main group at risk of severe dengue when they become infected again. For this reason, it’s rare for travellers to develop severe dengue.
The warning signs of severe dengue usually appear three to seven days after the original symptoms, and include:
- fever decreasing
- an intense and persistent abdominal pain
- persistent vomiting and blood in your vomit
- rapid breathing
- bleeding gums
- feeling tired
Another related complication is that people with sever dengue can experience a sudden and severe drop in blood pressure. This is known as dengue shock syndrome.
Symptoms of dengue shock syndrome include:
- cold, clammy skin
- a weak rapid pulse
- dry mouth
- reduced flow of urine
- fast breathing
If you have any of the symptoms of severe dengue, you should seek immediate medical help to prevent the disease progressing.
Call 999 and ask for an ambulance.
You will probably need to be admitted to hospital and given fluids via a drip into one of your blood vessels to prevent dehydration and stabilise your blood pressure.
With treatment, the vast majority of people make a rapid recovery and are usually well enough to leave hospital after a few days. Without treatment, severe dengue is fatal in up to 40% of cases.
There is no vaccine to prevent dengue. The best way to prevent getting the disease is to avoid being bitten by an infected mosquito.
Avoid being bitten by a mosquito by:
- using insect repellent to avoid being bitten, especially around dawn and dusk – products containing N-diethylmetatoluamide (DEET) are effective, but products containing this ingredient should not be used in babies younger than two months and in lower concentrations in younger children (20-30% DEET)
- wearing loose-fitting but protective clothing – mosquitoes are able to bite through tight-fitting clothes; trousers, long-sleeved shirts, and socks and shoes (not sandals) are ideal
- sleeping under a mosquito net to avoid being bitten at night
- be aware of your environment – mosquitoes that cause dengue breed in standing water in crowded urban environments; this can range from communal toilets to water that gathers inside a stack of old tyres
Read more about preventing insect bites.
‘I wouldn’t want to repeat the experience of having dengue’
Hugh Wilson didn’t know anything about dengue until he came down with the illness on holiday in Thailand.
“I never seemed to get bitten while I was travelling,” says Hugh. “I wasn’t really concerned about mosquitoes.”
Hugh and his partner were staying in Krabi in southern Thailand when Hugh started to experience symptoms.
“It started off as a mild headache and then fever. I also had a rash of tiny red spots over my shoulders, chest and back. The fever was awful but the worst thing was the headache. It was the worst headache I’d ever had, like torture. Painkillers didn’t have any effect and it was worse when I tried to sleep. So I got no sleep at all, which was horrible.”
Hugh was staying on a small island only accessible by boat. He suffered for three days and nights before he sought medical help.
“I was first seen by a nurse attached to one of the hotels on the island. She looked at me and said she wasn’t equipped to diagnose me. I realised I was going to have to get back on a boat and get help on the mainland. I was too weak to carry my rucksack so thank goodness my partner was there to help me.”
Hugh went to the nearest hospital. The doctors gave him blood tests. At first, they were unable to confirm the dengue virus, but there had been a recent outbreak of the disease.
“They told me to come back in two days if I wasn’t feeling any better and to take paracetamol. But that night I just felt awful and went back the next day. They admitted me and did other tests which confirmed it was dengue.
“Luckily, I didn’t have any dangerous complications. They gave me an injection which I think may have been a muscle relaxant, but the language barrier was difficult to overcome. I just let things happen.
“I felt very relieved that I was in hospital and someone was looking after me.”
Hugh stayed in hospital for two nights and three days. He started feeling a lot better after the first day. Doctors monitored his condition. They told him the fever had peaked and the worst was over.
Hugh left hospital feeling much better. “I was incredibly weak for weeks afterwards,” he says. “All I could do was wander around and try to keep out of the sun. We went to Bangkok a week later and I collapsed after drinking three pints of beer. It took a while to recover.”
Hugh says he’ll never be casual about bite protection again.
“I wouldn’t ever want to repeat the experience of having dengue,” he says. “I wish I’d known more about dengue. The real fear seemed to be malaria. But after I’d had dengue, I found out it’s a big problem but just not as well known as malaria. We had mosquito nets and coils, which we only used at night. We were quite slack about putting on repellent during the day. But now I’ve learned my lesson.”