Dengue

Introduction

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 41ºC (105.8ºF)
• headache
• pain behind the eyes
• bone, muscle and joint pain Call a doctor if you develop a fever or flu-like symptoms within two weeks of returning from an area where the dengue virus is common.

Read more about the symptoms of dengue.

What causes dengue?

Dengue is spread by a type of infected mosquito called 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, typically areas that have a combination of:

• a warm and humid climate
• overcrowding and major urban centres

Dengue cannot be spread from person-to-person.

Read more about the causes of dengue

Diagnosing dengue

If you have travelled to a country with dengue and develop symptoms after you return home, go straight to your nearest healthcare professional (either a doctor 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.

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 if the dengue virus is present in your bloodstream.

Treating dengue

Dengue usually clears up by itself within around 1-2 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.

Complications

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.

Prevention

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 and night

Read more about reducing your risk of getting dengue.

Who is affected

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.

Anyone can get dengue.

Symptoms

Symptoms usually develop from 3-14 days after being exposed to the dengue virus (the incubation period); the average incubation period is around 4-7 days.

Symptoms usually begin with a sudden high temperature (fever) which can reach as high as 41ºC (105.8ºF).

Other symptoms include:

• severe headache
• eye pain; specifically pain behind the eyes
• severe aching in your bones and joints (dengue is also known as ‘breakbone fever’)
• severe muscle pain (myalgia) of the lower back, arms and legs
• abdominal pain, feeling sick and being sick
• chills (shivering)
• flat red skin rash
• facial flushing
• loss of appetite
• sore throat
• abnormal bleeding, such as nosebleeds, bleeding gums and/or blood in your urine

Symptoms usually pass within a couple of weeks, but it can take several more weeks to make a full recovery. It is common to feel very tired when recovering from this type of infection.

When to seek medical advice

You should see your doctor if you develop a fever or flu-like symptoms within two weeks of returning from an area where the dengue virus is common - such as South East Asia, the Far East and the Indian Subcontinent.

There is little your doctor can do to speed up the course of the infection, but it is important to get your condition diagnosed in case there is a more serious cause of your symptoms.

Causes

Dengue is spread by a type of infected mosquito called the Aedes aegypti mosquito. The mosquito bites throughout the day and night.

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 then you should develop life-long immunity against that strain. But it is still possible to be infected again by a different strain.

If you are 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).

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.

Growing populations and an increase in global travel have resulted in the virus spreading between different groups.

The Aedes mosquito prefers to breed near water and is often found in stagnant water in containers around building sites in urban environments. Rates of dengue are often high in major cities in the developing world which have poor levels of sanitation.

Your risk of catching dengue increases if you plan to 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.

Treatment

There is currently no cure for dengue so treatment involves trying to relieve your symptoms and make you feel as comfortable as possible while the infection takes it course.

It is recommended that you:

• use the painkiller 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 3-5 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 back to normal.

If you are worried about any aspect of your treatment or diagnosis when abroad, see your doctor when you get home. Make sure you tell them where you have been, what your symptoms were, and what treatment you received.

Prevention

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 through the day and night to avoid being bitten – products containing N-diethylmetatoluamide (DEET) are effective, but products containing this ingredient should not be used in babies younger than two years old

• 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 tires

Read more about preventing insect bites.

Complications

In a small number of cases a person with dengue goes on to develop a more serious and potentially life-threatening form of the condition known as severe dengue.

Exactly why this is the case is unclear, but the main risk factor is having had a history of previous dengue infection.

Signs and symptoms of severe dengue include:

• the fever often disappears
• feeling tired
• an intense and persistent abdominal pain
• persistent vomiting (being sick)
• swelling of your liver which can be both painful and noticeable to the touch
• passing large amounts of blood in nose bleeds, heavy periods, passing red urine with your stools (‘poo’) and/or vomiting blood

Another related complication is that people with severe 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 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.