Dengue fever could spoil your holiday destination

Outbreaks of dengue fever (also called 'breakbone fever') now occur in a growing number of popular holiday destinations, including northern Australia and many Pacific Islands. An updated dengue fever warning was posted on the government’s 'safe travel' website in November 2011. There is no vaccine against dengue fever, or specific treatment for it, so taking precautions against mosquito bites and trying to reduce mosquito numbers are key for those travelling to dengue-prone areas. A more severe form, dengue haemorrhagic fever (DHF), can be fatal and requires urgent medical treatment.

How many are affected?

From 2006 to 2010 there were 436 cases of dengue fever in New Zealand. This total includes 51 cases in 2010, 139 cases in 2009 and 113 cases in 2008. New Zealand currently does not have the mosquito species responsible for spreading dengue fever, so the cases represent people who have been infected with dengue overseas. (However, there is always a potential for exotic mosquitoes to get into the country and become established here, which would open up the possibility of diseases such as dengue being spread within New Zealand.)

Dengue spreading worldwide

The World Health Organization (WHO) estimates that 40% of the world’s population is now at risk of contracting dengue fever. It is established in over 100 tropical and sub-tropical countries, with South-East Asia and the Western Pacific cited as two of the worst-hit areas. The disease is particularly prevalent in urban areas where standing water is near to homes and provides an ideal breeding ground for the carrier mosquitoes.

Areas where dengue may occur

Destinations reported to be affected [Nov 2011] include:

• North Queensland, Australia
• Cook Islands
• Fiji
• Marshall Islands 
• Kiribati
• New Caledonia
• Palau
• Samoa
• Tonga
• Vanuatu
• Asia (including India)
• Latin/South America.

Dengue outbreaks can occur anywhere in tropical countries, however, so caution is always advisable.
See www.safetravel.govt.nz for latest updates and general travel alerts.

What is dengue fever?

Dengue fever is a viral infection which is transmitted via the bite of particular breeds of mosquito. It can cause severe flu-like symptoms and, sometimes, a potentially fatal complication called dengue haemorrhagic fever. There is no medical treatment for the disease, nor is there a vaccination, so preventing mosquito bites is the best form of protection.

Symptoms of dengue fever

Symptoms of dengue fever tend to develop within four to seven days of being bitten by the infective mosquito. It cannot be spread directly from person to person. Doctors can usually diagnose dengue fever based on a physical examination and a blood test.

Typical symptoms of dengue fever include: 

• sudden onset of fever (lasting three to seven days) 
• intense headache and pain behind the eyes
• muscle and joint pain - particularly affecting the back, ankles, knees and elbows 
• loss of appetite
• vomiting and diarrhoea
• skin rash
• minor bleeding from the nose and gums 
• extreme fatigue.

Dengue haemorrhagic fever

Dengue haemorrhagic fever (DHF) is a rare, severe and sometimes fatal form of dengue fever. It appears that people who have previously been infected with another strain of dengue fever are more at risk from this complication. Initially, DHF presents in the same way as classical dengue fever but after a few days the person’s condition worsens rapidly and he or she collapses. Large bruises often appear on the skin and there can be bleeding from the nose, gums or bowel. It is important to get urgent medical treatment if these symptoms appear.

Treatment and recovery

Dengue fever
There is no specific medical treatment for dengue fever. People are advised to rest, drink plenty of fluids and take paracetamol for pain. Aspirin and ibuprofen are not recommended for relieving the pains of dengue fever because these drugs might increase the risk of bleeding problems sometimes seen with dengue infections. Occasionally, people are admitted into hospital for observation and care. In general, most people recover fully from dengue fever, but this can sometimes take months and recovery can be made more difficult by depression and fatigue. Many people infected with dengue fever have only a mild illness and often are not even aware they have been infected.

Dengue haemorrhagic fever (DHF)
According to the World Health Organization, for those who develop DHF, without treatment about 20% of people die from complications. With appropriate treatment by health professionals experienced in caring for people with the disease, this can be reduced to 1%. The WHO also reports (2009) that DHF is a leading cause of serious illness and death among children in some Asian countries.

Prevention of dengue fever

There is no vaccine to prevent dengue fever. It is spread by certain breeds of mosquito that carry the infection from human to human. The best way to avoid infection in areas where dengue-carrying mosquito populations are established, is to protect yourself against being bitten and reduce potential mosquito breeding sites.

To protect against mosquito bites 

• Wear loose-fitting, light-coloured clothing that covers up as much of the body as possible, especially around dawn and dusk when mosquitoes are usually most active. If conditions are favourable the mosquito (especially dengue-carrying mosquito) will continue biting throughout the day. The mosquito that transmits dengue is commonly found in urban areas, so avoiding rural travel will not protect you against dengue. 
• Use insect repellents containing either DEET, or icaridin (previously called picaridin). DEET should be of 30% concentration or more. Recently, up to 30% DEET has been approved for use in children over the age of two months.
• Use insect screens and mosquito nets (although this will have less of an impact on the day-biting dengue-carrying mosquito than the night-biting malaria-carrying mosquito).
• In parts of the world where both dengue fever and malaria occur, mosquito avoiding measures will need to be adhered to 24 hours a day.

For more tips on avoiding insect bites, see our travel health checklist.

Dengue-carrying mosquitoes generally breed in stagnant water found in man-made containers (eg, discarded tyres, uncovered barrels, buckets) rather than in rivers, swamps, open drains, creeks or mangroves. To eliminate breeding sites, empty any containers that hold water in and around the place you are staying.

Get checked if unwell after travel

Anyone who is ill after returning from a dengue-prone area [or from overseas travel] should contact their GP so they can be assessed, get treatment where needed and be monitored for complications. It is advisable to phone your doctor's surgery before going in and tell them which countries you have travelled to, in case you have an infectious disease.

You can also phone Healthline, free (in NZ) on 0800 611 116 for advice. Healthine is staffed by registered nurses or other health professionals.

Related topics

Also see: Mosquitoes - how could a disease outbreak occur in NZ? and Travel vaccinations

Original material provided by everybody. Kindly reviewed by Dr Jenny Visser from the Travel Doctor clinic, Wellington, May 2009. Updated by everybody, November 2011.