DENGUE FEVER

With thanks to Dr. Marc Shaw of the Traveller's Health Centre 72 Remuera Road, New Market, Auckland 09-520-5830 & Dr. Geoff Kivell (The Floating Doc) S/V "Aspect of Arran"

Disclaimer: 

Whilst every effort is made to provide current and accurate information and advice,  no liability is accepted by the Island Cruising Association for any incorrect statement or advice.

What is Dengue Fever?

Dengue and Dengue Haemorrhagic Fever (DHF) are caused by one of four closely related virus 'serotypes' from the same family of viruses. Infection from one serotype of Dengue Fever virus provides immunity to that 'type', but does NOT provide cross ­protective immunity to other 'types', so persons living in a Dengue Fever area can have four dengue infections during their lifetimes.

Infection with a Dengue Fever virus serotype can produce a spectrum of illness from a 'viral syndrome' to a severe and fatal bleeding disorder called Dengue Haemorrhagic Fever (DHF). Important risk factors for DHF include age (the young are worse off than older people) and an immune status that is compromised or reduced.

Where does Dengue Fever occur?

Dengue Fever is primarily an urban disease of the tropics. There are three areas world­wide that are currently at increased risk for travellers getting the disease: Western Pacific, South East Asia, Eastern Seaboard of Central and South America.

How do you catch Dengue Fever?

Dengue Fever is transmitted by the bite of an infected mosquito. The viruses that cause it are maintained in a cycle that involves humans and a domestic day­biting mosquito that prefers to feed on humans. Once infected, a mosquito remains infective for life.

The dengue fever mosquito (Aedes aegypti) is dependent on humans and never lives more than 90 metres from dwellings, thus guaranteeing her meals. The sound of her wings cannot be heard and she attacks from below or behind, e.g. underneath chairs and mainly at the feet and ankles.

The females are very nervous feeders, disrupting the feeding process at the slightest movement only to return to the same or a different person to continue feeding moments later. Because of this behaviour the mosquito will often feed on several persons during a single blood meal and, if infective, may transmit the dengue virus to many people in a short time. It is not uncommon to see several members of the same household become ill with dengue fever within a 24­36 hour frame, suggesting that a single infective mosquito infected all of them.

What is the incubation period (time from exposure to first symptoms)?

The clinical features of Dengue Fever vary according to the age of the patient. These may develop as soon as 5­7 days after infection.

Signs and symptoms of Dengue Fever.

Infants and young children may have a fever with a rash. Older children and adults may have a combination of any of the following:

• flu­like illness
• high fever and chills
• shaking sweating severe headaches
• severe pain behind the eyes
• extreme muscle and joint pains ( hence the name 'breakbone fever')
• generalised rash over the body
• bruising and bleeding on the limbs, face and trunk
• vomiting or passing blood.

What is the treatment?

The only treatment is to manage the affected person with fluids and pain relief. There is no treatment available.

How do you prevent Dengue Fever?

1. Minimise mosquitoes: To minimise mosquito bites it is obvious that mosquito­prone areas (such as vessels holding water, discarded cans and bottles, and old tyres half submerged in swampy water) should be avoided.

2. Understand the basic behaviour and feeding habits of the mosquito carrier: The adult mosquito prefers to live indoors and feed on humans during 2 peaks of biting activity: early morning for 2­3 hours after daybreak and in the afternoon several hours before dusk. They can, however, feed all day long indoors as well as and on overcast days.

3. Screen or air­condition rooms

4. Burn mosquito coils in the immediate area. CAUTION is recommended here as breathing problems or even asthma may develop, although rarely. Electric plug chemicals will also help to repel mosquitoes from a room.

5. Avoid perfumes: mosquitoes are attracted to scents.

6. Wear long sleeves and pants and avoid dark clothes: Light coloured clothing should cover the arms and legs.

7. Spray a "knock down" insecticide in sleeping and living areas at dusk.

8. Use a skin­spray insect repellent. 80% DEET (N,N-diethyl-m-toluamide) may be used by adults, but should not be applied to babies and only sparingly (quick sprays, 2-3 in 24 hours) to children 6-24 months because of the potential for toxic effects. 25-30% DEET, lasting 4 hours is available. Children and pregnant women are recommended to use a natural insect repellent with citronella or eucalyptus.
   
   DEET WARNING:
   
   * may damage synthetics / watch faces etc.
   * may cause irritation to skin and eyes.
   * rarely associated with neurological side-effects, especially in children.
   * wash hands after applying.
   * avoid lips, eyes, sunburned skin

9. Permethrin is an insecticide that can be used to soak mosquito nets and protective clothing. Permethrin treatment kits are available and one application will last 6 months.

Dengue Fever is preventable, but no prevention is 100% effective.

Disclaimer:

Whilst every effort is made to provide current and accurate information and advice, no liability is accepted by MASTA New Zealand or its clinical subsidiary (Worldwise Travellers Health and Vaccination Centres of New Zealand) for any incorrect statement or advice.