Mosquitos and black flies in a disaster

Mosquitos

Mosquito numbers can increase after severe weather events as standing water from heavy rainfall and flooding provides the perfect conditions for mosquito breeding. Increased numbers of mosquitoes lead to an increased risk of being bitten and contracting mosquito-borne diseases.

The most common mosquito-borne diseases in Queensland are caused by Ross River and Barmah Forest viruses. Outbreaks of dengue have been reported annually in north Queensland. A strain of West Nile virus called Kunjin virus, Zika virus and Murray Valley encephalitis (MVE) have also rarely been reported.

The incubation period for mosquito-borne diseases varies. Symptoms are usually present 3–15 days after being bitten by an infected mosquito. Common signs and symptoms are:

  • headache
  • fever
  • joint or muscle pain
  • skin rash
  • fatigue
  • nausea.

Prevent breeding around your home

One of the best ways to prevent mosquito-borne diseases is to prevent mosquitoes from breeding. You can reduce mosquito breeding around the home by:

  • cleaning up around your house and yard following a cyclone or flood once it's safe to do so
  • wherever possible, remove any pools of standing water, including clearing debris from ditches, cutting small channels to drain pooling water, or filling in holes.
  • cleaning up debris deposited on your property by flood waters or cyclones. Debris and rubbish often pool enough water to produce large numbers of mosquitoes
  • checking the integrity of mosquito-proof screens on and rainwater and bore water holding tanks replace as required.

Personal prevention

There are several measures you can take to avoid being bitten by mosquitos:

  • apply insect repellent containing DEET or Picaridin on exposed skin and reapply as required (follow the instructions on the repellent), especially when outside at dawn or dusk
  • in dengue receptive areas (north Queensland) protect against mosquito bites during the day as the dengue mosquito bites during the day and likes to rest indoors
  • wear long, loose, light-coloured clothing and closed-in footwear
  • use flying insect spray, mosquito coils (outside) or plug-in insecticide devices to kill mosquitoes indoors
  • use bed, cot, and pram mosquito netting as required
  • check that the flyscreens in your home are in good condition.

Black flies

The number of black flies (Austrosimulium) can increase following a flood or heavy rain, particularly in inland areas. While black flies do not transmit disease, allergic reactions and bacterial skin infections may occur from bites and scratching the bites.

Black flies are aggressive biters that are found in areas around streams and rivers. They breed in running water— but once flood water recedes the number of black flies rapidly decrease. Black flies are active only during the day and do not bite at night. Their peak activity period tends to occur early morning and late afternoon.

Signs and symptoms

The range of signs and symptoms associated with bites can include:

  • painful, itchy bite lesions
  • urticaria (itchy raised skin rash)
  • cellulitis (hot, red, swollen and painful skin and underlying tissue infection).

Prevention

Black fly bites can be avoided by:

  • apply insect repellent on exposed skin and reapply as required (follow the instructions on the repellent), especially when outside at dawn or dusk
  • wear long, loose, light-coloured clothing and closed-in footwear
  • use flying insect spray, or plug-in insecticide devices to kill black flies indoors
  • use bed, cot, and pram mosquito netting as required
  • check that the flyscreens in your home are in good condition.

Treatment

Black fly bites should be managed to prevent secondary skin infections:

  • apply calamine lotion or another anti-pruritic preparation to bite areas to prevent itching
  • if bite areas become inflamed, clean with soap and water at least once daily, apply an antiseptic lotion and keep covered with a dry dressing
  • keep affected limbs elevated
  • wash hands before and after touching open wounds
  • observe skin sores. If skin sores become hot, red, swollen and painful, seek medical attention immediately.

Further information

  • Call 13 HEALTH (13 43 25 84) at any time.
  • Contact 13 QGOV (13 74 68) for your nearest Public Health Unit.
  • If you or anyone in your household is experiencing any health effects, seek medical advice from your doctor.

Download the protect yourself against mosquitoes factsheet (PDF 478 kB).

Last updated: 4 January 2024