Dengue fever

Dengue fever is a viral infection carried by mosquitoes. It is increasingly widespread around the world and is common in various travel destinations popular with New Zealanders, including South East Asia and the Pacific Islands.

Up to 400 million people are infected each year in tropical or sub-tropical countries around the world. In New Zealand, 161 cases of dengue fever were reported in 2017, all of which were contracted overseas.

Dengue fever has never been acquired in New Zealand, as New Zealand does not have the variety of mosquito that carries the virus. However, it is one of a number of nasty travel diseases that New Zealanders should take precautions to avoid.

Transmission of the virus

Dengue fever is caused by infection with one of four strains of dengue virus. The virus cannot be passed directly from one infected person to another. Dengue fever is a mosquito-borne infection that requires a specific variety of mosquito to pass it from person to person. The mosquito transmits the virus by biting an infected person (allowing the virus to enter the mosquito) and then biting an uninfected person (allowing the virus to enter that person’s bloodstream).

The incubation period (the time between infection with the virus and appearance of symptoms) is, on average, five to eight days.

Symptoms

Dengue fever can range in severity from a mild flu-like illness, to a condition that produces severe, debilitating symptoms (severe dengue).

The onset of symptoms is usually sudden and initial symptoms commonly include:

• High fever (up to 40°C)
• Rash (red with dots and blotches)
• Headache
• Pain in the muscles and joints - particularly in the legs
• Pain behind the eyes - particularly when moving them
• Nausea and vomiting
• Red eyes
• Enlarged lymph nodes
• A red flush to the face
• Lower back pain
• Severe weakness and 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 one of the four strains of dengue fever, the body is immune to that strain of the virus, and temporarily immune to the other strains for about a year. Subsequent infection with one of the other dengue fever strains tends to produce more severe symptoms than initial infections.

Complications

The most serious complication of dengue fever is when the condition progresses to severe dengue (previously known as dengue haemorrhagic fever). Severe dengue 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. Severe dengue is fatal in approximately one in every 20 infected individuals.

People who have previously been infected with dengue fever are at an increased risk of developing severe dengue if they contract the virus again.

Diagnosis

When making a diagnosis of dengue fever a doctor will ask whether the patient 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.

Treatment

There is no specific drug treatment for dengue fever. Because dengue fever is caused by a virus, antibiotics are of no benefit in combating the infection.

Treatment will aim to reduce the severity of symptoms:

• Rest
• Adequate fluid intake to prevent dehydration due to vomiting and fever
• Pain-relieving medications such as paracetamol, which can help to relieve discomfort and to reduce the fever. Non-steroidal anti-inflammatory medications (NSAIDs) such as aspirin and ibuprofen should be avoided as they can increase bleeding.

In cases of severe dengue, hospitalisation and treatment with intravenous fluids or transfusions of blood or blood products may be necessary, particularly if bleeding is severe.

Prevention

There is no vaccine for dengue fever and, in contrast to malaria, there are no drugs that can be taken to prevent infection while travelling in parts of the world where dengue fever is prevalent.

Prevention involves avoiding being bitten by mosquitoes while in regions where dengue fever occurs.

The following measures can protect against acquiring dengue fever:

• Wear clothing/hats that cover the arms, legs, and head
• Wear shoes rather than sandals or jandals
• Apply insect repellent to exposed skin. The most effective repellents contain DEET (diethyl toluamide) at a concentration of 30–50%
• Apply permethrin insecticide to clothes and shoes
• Sleep under mosquito nets treated with permethrin
• Use electric insect-repellent devices or mosquito coils
• Try to stay in accommodation that has insect screens on doors and windows or is air-conditioned.

Further information and support

For further information and support about dengue fever contact your doctor, a travel health specialist, or Healthline (Freephone: 0800 611 116).

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.

References

Auckland Regional Public Health Service (2018). Dengue fever fact sheet (PDF). Auckland: Auckland Regional Public Health Service – Auckland District Health Board. http://www.arphs.health.nz/find/results?Search=dengue+fever&action_results=
Mayo Clinic (2018). Dengue fever (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/dengue-fever/symptoms-causes/syc-20353078 [Accessed: 15/01/20]O’Toole, M.T. (Ed.) (2017). Dengue fever. Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.
DermNet New Zealand (2017). Dengue fever (Web Page). Hamilton: DermNet New Zealand Trust. https://www.dermnetnz.org/topics/dengue/ [Accessed: 15/01/20]
Health Intelligence Team (2017). Notifiable diseases in New Zealand: Annual Report 2017 (PDF). Porirua: Institute of Environmental Science and Research Ltd. https://surv.esr.cri.nz/PDF_surveillance/AnnualRpt/AnnualSurv/2017/2017AnnualNDReport_FINAL.pdf Ministry of Health (2018). Dengue (Web Page). Wellington: New Zealand Government Ministry of Health. http://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/sore-throat [Accessed: 15/01/20]
World Health Organisation (2020). Dengue and severe dengue. https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue [Accessed: 30/03/20].

Last Reviewed – March 2020

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