Dengue fever

Dengue fever is a viral illness caused by infection with 1 of 4 types of the dengue virus. When a person recovers from dengue infection they develop a long-term (not always lifetime) immunity to that type, but not the other 3 types.

If the person is infected again with a different virus type, they may develop the more severe form of the illness known as dengue haemorrhagic fever (DHF).

How it is spread

It is spread by the bite of an infected dengue mosquito (usually the Aedes aegypti species).  There is no spread from human to human.

Where and when it is found

Dengue fever occurs in tropical and sub-tropical areas of the world, including north Queensland.

Although the mosquito capable of spreading dengue is found in Queensland as far south as Roma in the inland and Gladstone on the coast, and as far west as Camooweal, the area at particular risk for acquiring dengue is coastal to sub coastal Queensland north of Bowen.

Aedes aegypti mosquitoes have not been established in the Northern Territory (NT) since the 1950s and there has been no dengue fever transmitted in the NT since then.

The mosquito is imported periodically into Darwin on overseas vessels such as foreign fishing vessels and cargo ships, but has been detected and eliminated each time.

Dengue mosquitoes were imported into Tennant Creek from Queensland in 2004 and 2011 and on Groote Eylandt in 2006. Surveys continue in the NT to ensure early detection and identification of any importation of the dengue mosquito.

For the past 60 years all persons notified with dengue fever in the NT have been interviewed to confirm that the disease was acquired in known dengue endemic areas overseas or in north Queensland.

Between 2003 and 2013 there have been 404 cases of dengue notified in the NT.

These were acquired mostly in Indonesia or East Timor.

Mosquito surveys by the Department of Health continue to ensure that knowledge about the presence of any exotic mosquito population remains current.

Symptoms

It usually takes 3 to 14 days (commonly 4-7 days) between getting bitten by a dengue virus infected mosquito and becoming sick.

Dengue fever

Dengue fever is more commonly seen in older children and adults. It is characterised by abrupt onset of high fever lasting 3-7 days, severe frontal headache, pain behind the eyes and muscle and joint pains. Other symptoms may include loss of appetite, nausea, vomiting and diarrhoea, a blanching rash and sometimes minor bleeding (eg from nose and gums).

The acute symptoms of dengue fever last up to 10 days. Some people may experience repeated episodes of fever.

Full recovery may be slow and associated with weakness and depression. It is rarely fatal.

Dengue haemorrhagic fever

DHF is most commonly seen in children under 15 years of age but can also occur in adults. It begins with the same symptoms as dengue fever but is followed by rapid deterioration, bleeding and cardiovascular collapse 2-5 days later.

The duration of DHF depends on the severity of the illness and response to treatment. It can be fatal.

Treatment

There is no specific treatment or vaccine. Supportive treatment includes plenty of oral fluids and paracetamol for relief of fever and body aches and pains.

Aspirin and non-steroidal anti-inflammatory drugs should not be used as they can affect blood clotting.

Anyone with DHF should be hospitalised for fluid replacement and observation.

Things to know about dengue mosquitoes

Only the female mosquito transmits the virus. They are most active during daylight hours. They rest indoors in closets, behind curtains and other dark places. Outdoors they rest where it is cool and shaded.

Breeding sites are mainly around the home in containers that can hold water. The mosquito rarely flies more than 200 metres from its breeding site. They do not breed in dirt pools on the ground, swamps or dirt storm water drains.

The eggs of the mosquito capable of transmitting dengue are drought resistant and can last over 12 months in receptacles that have previously held water. The carriage of pot plant saucers, old tyres and any formerly rain filled receptacles from north Queensland, where dengue mosquitoes exist, could introduce the mosquito the NT.

How to avoid getting dengue fever

Be aware of countries or areas where dengue fever is endemic.

In our region dengue fever is well established in northern Queensland, southern Cambodia, China, Indonesia, Laos, Malaysia, Myanmar, Papua New Guinea, the Philippines, Thailand, Timor Leste and Vietnam.

Make sure to take appropriate clothing and insect repellent to these areas when travelling.

Residual spray

Barrier sprays such as outdoor barrier surface spray or similar can be purchased from supermarkets or applied by pest companies to kill adult mosquitoes harboured in or near the house.

This is a residual surface treatment for use in dark sheltered areas or dark objects inside houses such as behind wardrobes or cupboards, under tables and chairs, and behind or on curtains. It can be sprayed on outdoor dark sheltered surfaces close to a house such as under wash troughs, in accumulations of rubbish or equipment, and in corners on verandahs.

Precautions on any treatment should be read before application.

Personal protective measures

• avoid areas of likely mosquito activity
• ensure flyscreens in houses, caravans and tents are in good condition
• use protective clothing in outdoor situations including covering feet, legs and arms. Loose, light coloured clothing is best
• use personal repellents containing DEET, picaridin or PMD (extract of lemon eucalypt) on areas of exposed skin in combination with protective clothing. Repellents only protect against mosquito bites for up to 4 hours, not all night
• use electric insecticide devices using repellent treated pads in indoor or enclosed areas
• use mosquito coils, or candle heated or gas operated devices using insecticide treated pads for patio and veranda or relatively sheltered or low wind outdoor situations.

For more information on protection measures go to personal protection from mosquitoes.

How to prevent dengue fever from being established in the NT

Avoid importing or spreading mosquitoes

Spray any container or receptacle that has previously held water in north Queensland with a residual surface spray insecticide, or wipe thoroughly with a strong bleach or chlorine solution. Do not spray current eating or drinking utensils.

Eliminate potential breeding sites

• empty and apply surface spray to any old unused container that has held water eg tyres, plastic containers, black sheet plastic or pot plant drip trays. Store any containers upside down and undercover or under a domed tarpaulin in good repair
• avoid using saucers or drip trays under pot plants. Let pots drain directly onto the ground or make sure saucers are emptied at least once/week. Wipe their inner surface firmly with a cloth several times or fill with sand, or apply surface spray or methoprene insecticide pellets
• empty bird baths and pet drinking water at least weekly and wipe as above, or use methoprene pellets
• cover and completely seal septic tanks, rainwater tanks or other large water storage containers. Use methoprene briquettes in unsealed tanks as a temporary measure
• dispose of rubbish around the yard that may collect water eg plastic sheets or old tarpaulins, pot plant holders, old wheelbarrows, old tyres, and plastic containers of any type
• ensure roof gutters drain freely so that pools of water are not left at any low points. Throw a small amount of methoprene pellets on to the roof above problem gutters
• fishponds with fish do not breed mosquitoes. Tadpoles do not eat mosquito larvae. Keep fishponds and frog ponds stocked with fish and do not spray surface spray onto or at the edge of fishponds.

Information for health professionals

To find out more go to the NT Health website.

Contact

For more information contact your nearest Centre for Disease Control.