Dengue fever

Dengue fever is caused by the dengue virus which is spread through the bite of particular breeds of mosquito (Aedes mosquito). These mosquitoes are prevalent in Pacific Island countries, Asia, Central and South America, and Africa, and are commonly found in cities and urban areas. This mosquito is not present in New Zealand. Although the most common time for mosquito bites is early morning and late afternoon, dengue-carrying mosquitoes bite all through the day. 

Mosquitoes become infected with dengue after biting sick humans who have dengue virus in their blood. If an infected mosquito later bites another human, it can pass on the dengue virus. There are 4 types of dengue viruses known to cause disease in humans. A person infected with one type of dengue will only become immune to that type. They will not be immune to other types of dengue and could be at higher risk of severe disease if they later contract another type.

Dengue fever cannot be spread directly from person to person.

Symptoms of dengue fever tend to develop within 4–7 days of being bitten by the infective mosquito.

The common symptoms of dengue are:

• sudden fever
• severe headache
• pain behind your eyes
• feeling very tired
• muscle and joint pain (ankles, knees, elbows)
• rash on your arms and legs, severe itching, your skin peeling 
• nausea (feeling sick) or vomiting (being sick).

Dengue fever is sometimes described as being similar to a severe flu-like illness, and may also be referred to as ‘breakbone fever’ because of the severe muscle and joint pain. Generally, younger children and those with their first dengue infection have a milder illness than older children and adults.

Severe dengue or dengue haemorrhagic fever

In rare cases, dengue fever can worsen to severe dengue, which can result in shock, severe bleeding, organ failure and even death. You are at greater risk of this if you have had dengue fever before and are infected with a different strain of the virus. This is important if you make a number of visits back to a dengue-affected country over the years, as you are at risk of picking up dengue fever repeatedly. Initially, severe dengue has the same symptoms as dengue fever, but after a few days, your condition worsens rapidly.

See a doctor immediately if you think you may have dengue fever. Early diagnosis can help to reduce the risk of complications. Your doctor will ask about your symptoms and any recent travel, and will do a physical examination. Blood tests are required to diagnose dengue fever.  

Most people infected with dengue will only have a mild illness and may not even be aware they have been infected. There is no specific medical treatment for dengue. 

Your doctor may advise you to:

• have bed rest
• drink plenty of fluids
• take medicines such as paracetamol to reduce fever and ease pain. Do not take aspirin or non-steroidal anti-inflammatory agents such as ibuprofen, naproxen or diclofenac because they can increase the risk of bleeding. 

The illness usually lasts up to 10 days but recovery may take some time; you may feel tired and depressed for weeks. 

For people who show warning signs of severe dengue, hospital admission is required. Treatment may include drips (intravenous fluids and replacement of lost electrolytes).

For most travellers, there is no suitable vaccine to prevent dengue. The best way to avoid infection in areas where there are dengue-carrying mosquito populations is to protect yourself against being bitten and to reduce potential mosquito breeding sites. All people in dengue-affected areas, whether you have been previously infected or not, should take precautions to prevent being bitten.

A new vaccine for dengue has been approved in some countries where dengue fever is common. It is only useful for people who have previously been infected with dengue fever, as it can actually increase the risk of severe dengue for people who have never had the disease before. This vaccine is not routinely (or widely) available in New Zealand. Please see your local travel medicine specialist for further advice.

Protect against mosquito bites indoors

• Use screens on doors and windows.
• Use insect sprays.
• Use mosquito coils.
• Use a mosquito net over your bed at night. New bed nets often have insecticide already on the net but, if not, you can spray the net with insecticide.
• Turn on air conditioning if you have it and close all windows and doors – this is very effective at keeping mosquitoes out of the room.   

The dengue-carrying mosquito can be around during the day so keep covered day and night.

Protect against mosquito bites outdoors

• Wear an insect repellent cream or spray containing no more than 50% diethyltoluamide (DEET) or 30% DEET for children. Higher concentrations are no more effective and can be harmful. Products containing 20–25% picaridin (also known as icaridin) or 30% lemon eucalyptus oil (also known as PMD) can also be used. Read more about insect repellents and how to use them safely.
• When using sunscreen, apply repellent over the sunscreen. 
• Wear light-coloured protective clothing such as long-sleeved shirts, long pants and hats.
• Wear clothing treated with an insecticide such as permethrin. Clothing can be bought pre-treated, or you can buy permethrin and treat your own clothes. Permethrin-treated clothing can be washed several times and still provide protection against insects. Regular insect repellent applied to clothes can also provide temporary protection, but must be reapplied at regular intervals.
• Wear shoes rather than sandals. 
• Use zip-up screens on tents.
• Avoid areas where mosquitoes are most active.

The mosquito that transmits dengue is commonly found in urban areas, so avoiding rural travel will not protect you against dengue fever.

Reduce mosquito breeding sites 

Dengue-carrying mosquitoes generally breed in stagnant water found in containers (eg, discarded tyres, uncovered barrels, buckets) rather than in rivers, swamps, open drains, creeks or mangroves. The disease is particularly common in urban areas where standing water is near to homes and provides an ideal breeding ground for the carrier mosquitoes. 

To eliminate breeding sites:

• empty any containers that hold water in and around the place you are staying
• cover all water tanks, cisterns, barrels and rubbish containers
• remove or empty water in old tyres, tin cans, bottles and trays
• check and clean out clogged gutters and flat roofs where water may have settled
• change water regularly in pet water dishes, birdbaths and plant trays
• trim weeds and tall grasses, as adult mosquitoes seek these for shade.

Video: Fight the bite, day and night

Dr Laupepa Va'a from the Ministry of Health talks about how people travelling overseas can avoid being bitten by mosquitoes that might carry diseases such as dengue fever. and Zika virus. This video may take a few moments to load.

(Ministry of Health, NZ, 2018)

Areas often affected with dengue fever include:

• North Queensland, Australia
• Pacific Island nations
• Asia (including Cambodia and India)
• Central and South America
• Sub-Saharan Africa. 

Dengue outbreaks can occur anywhere in tropical countries as shown in the map below, so if you are planning on travelling, check the risk level(external link)(external link) before you go. 

(external link)(external link)

Image: HealthMap

Key facts

• Dengue is a mosquito-borne viral infection.
• The infection causes flu-like illness, and occasionally develops into a potentially lethal complication called severe dengue. Severe dengue is more likely in those who have been infected with dengue previously..
• The global incidence of dengue has grown dramatically in recent decades. About half of the world's population is now at risk.
• Dengue is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas.
• There is no specific treatment for dengue/severe dengue, but early detection and access to proper medical care lowers fatality rates below 1%.
• Dengue prevention and control depends on effective vector control measures.
• A dengue vaccine has been licensed by several National Regulatory Authorities for use in people 9–45 years of age living in endemic settings. It is not for use in people who have never had dengue fever before, as it can increase the likelihood of severe dengue.

Epidemiology and management of dengue fever

Video: Dengue fever - Nancy Rihana, MD

This video may take a few moments to load.

 
(IDPodcasts, US, 2013)

Continuing education modules(external link) Centres for Disease Control and Prevention, US, 2020
CDC Yellow Book(external link) Centres for Disease Control and Prevention, US
Dengue and severe dengue(external link) World Health Organization, 2017 
Dengue vaccine – WHO position paper(external link) World Health Organization, 2018