Dengue fever is a viral infection carried by mosquitoes. It is generally a disease of the tropics and is common in Africa, South East Asia, the Pacific Islands, the Caribbean and the Americas.
Although it has existed for more than 200 years, dengue fever has never been acquired in New Zealand, as New Zealand does not have the variety of mosquito that carries the virus. However, New Zealanders travelling to tropical countries should be aware of the very real risk of contracting the disease and take precautions.
The New Zealand Public Health Surveillance Report shows that for the 12 months from February 2012 to January 2013 there were 88 cases of dengue fever reported in New Zealand. All were contracted overseas.
Transmission of the virus
Dengue fever cannot be passed directly from one infected person to another. It is a mosquito-borne infection that requires a specific variety of mosquito (the “Aedes egypti” mosquito) to pass it from person to person. The mosquito transmits the virus by biting an infected individual then biting someone else.
The incubation period (the time between infection with the virus and appearance of signs and symptoms) is, on average, five to eight days.
Signs and symptoms
Dengue fever can range in severity from a mild flu-like illness, to a condition that produces severe, debilitating symptoms. The onset of symptoms is usually sudden and initial symptoms commonly include:
- High fever
- Pain in the muscles and joints - particularly in the legs
- Pain behind the eyes - particularly when moving them
- Red eyes
- Enlarged lymph nodes
- A red flush to the face
- Lower back pain
- Severe weakness
- Severe fatigue.
After two to three days the fever reduces and significant sweating occurs. A day or so later the fever rises again and a red rash begins on the arms and legs, then spreads to the chest, abdomen and back. In addition, the palms of the hands and the soles of the feet become swollen and turn bright red.
Most people fully recover from dengue fever, although the weakness and fatigue may last for several weeks.
After infection with dengue fever, the body is immune to the condition for about a year. Subsequent infection with dengue fever tends to produce more severe symptoms than initial infections.
The most serious complication of dengue fever is when the condition progresses to dengue haemorrhagic fever. It most commonly occurs in children under the age of 10 years and is characterised by severe symptoms of dengue fever accompanied by bleeding from the gums, nose, bowel, and into internal organs. Bruising and blood spots under the skin may be present and pneumonia
and inflammation of the heart may occur. Dengue haemorrhagic fever is a severe condition that is fatal in approximately five percent of infected individuals.
Individuals who have previously been infected with dengue fever are at an increased risk of developing dengue haemorrhagic fever with subsequent dengue fever infections.
When making a diagnosis of dengue fever the doctor will ascertain whether a person has recently visited the tropics. The doctor will take a full history of the symptoms (including their severity and duration) and will perform a physical examination. The doctor will look for the characteristic combination of fever, rash and headache that occurs with dengue fever. This combination of symptoms is known as the “dengue triad”.
Because dengue fever can be confused with other conditions such as influenza
, measles, malaria or typhoid fever, the doctor is likely to take blood tests in order to definitively diagnose the condition.
As dengue fever is caused by a virus there is no specific treatment and antibiotics are of no benefit in combating the condition. Treatment is supportive and includes:
- Encouraging adequate fluid intake
- Pain relieving medications such as paracetamol - which can help to relieve discomfort and to reduce the fever. Aspirin and non-steroidal anti-inflammatory medications should be avoided however as these can increase bleeding.
In cases of dengue haemorrhagic fever, hospitalisation and treatment with intravenous fluids or transfusions of blood or blood products may be necessary, particularly if bleeding is severe.
There is no vaccine for dengue fever. Prevention involves avoiding being bitten by mosquitoes while in regions where dengue fever occurs. The Auckland Regional Public Health Service recommends the following measures to protect against acquiring dengue fever:
- Wear clothing/hats that cover the arms, legs and head
- Wear shoes rather than sandals
- Apply insect repellent to skin. The most effective repellents are those containing DEET (diethyl toluamide) at a concentration of between 30% and 50%
- Apply permethrin insecticide to clothes
- Use mosquito nets impregnated with permethrin
- Use electric insect-repellent devices or mosquito coils
- When possible, stay in accommodation that has screens on doors and windows or is air-conditioned.
Further information and support
For further information and support about dengue fever please contact your doctor or a travel health specialist.
The New Zealand Ministry of Foreign Affairs and Trade operates an official website - www.safetravel.govt.nz
- that provides advice and travel alerts for New Zealanders living or travelling abroad. The website's health alerts include advice of outbreaks of diseases such as dengue fever.
Auckland Regional Public Health Service (2011) Communicable disease fact sheet - Dengue Fever. Auckland.
Carson-DeWitt (2006) Dengue fever. The Gale Encyclopedia of Medicine. Third Edition. Jacqueline L. Longe, Editor. Farmington Hills, MI: Thomson Gale.
DermNet NZ (2012) Dengue and dengue haemorrhagic fever. New Zealand Dermatalogical Society Inc. www.dermnetnz.org/viral/dengue.html
New Zealand Public Health Surveillance Report (2013) National Notifiable Disease Surveillance Data. New Zealand Ministry of Health.
Last Reviewed – 15 March 2013