Mosquito-borne diseases in Australia: a workplace guide

The mosquito-borne diseases that matter most for Australian workers are Japanese encephalitis, Ross River virus, Barmah Forest virus, Murray Valley encephalitis, Kunjin (West Nile) virus and dengue. If your crew works outdoors, you have a duty to eliminate the risk where that's reasonably practicable, and to minimise it where it isn't. In practice that means assessing exposure, vaccinating where advised, removing breeding sites, using repellent, training workers and watching their health.

Mosquito activity follows the weather. Wet seasons and warm spells create breeding sites, and the season now starts earlier and runs longer than it used to. Your risk assessment should look at the season and your location, not just the task.

Which diseases affect workers?

Most of these viruses are spread by mosquitoes that bite both animals and people. Japanese encephalitis virus is the one that has moved furthest. It was once found mainly in northern Australia, but it's now been detected in pigs in parts of South-East Queensland, New South Wales, the Northern Territory, Victoria and South Australia.

• Japanese encephalitis (JE): Serious and sometimes fatal. There's no specific treatment, and vaccination is recommended for people at high risk of exposure, such as outdoor workers in areas where it's been detected.
• Ross River virus: The most common mosquito-borne disease in Australia. It causes fever, rash and joint pain that can last months. There's no cure, but symptoms can be managed.
• Barmah Forest virus: Usually milder than Ross River virus, with rash, joint pain and fatigue. Many people have no symptoms. Most recover within weeks.
• Murray Valley encephalitis: Rare, but it can cause severe brain inflammation. There's no vaccine or specific cure.
• Kunjin (West Nile) virus: Mostly found in northern regions. Most cases are mild, but severe infection can cause encephalitis or meningitis.
• Dengue: Not endemic to Australia, but the mosquito that carries it, Aedes aegypti, is found in parts of Queensland and northern New South Wales, so local cases can occur. No vaccine is generally available.

Symptoms vary, but a worker who's had mosquito exposure and develops fever, a rash, severe headache, joint pain or drowsiness should see a doctor promptly, and tell them about the exposure.

What are your duties as a PCBU?

The WHS Act requires the person conducting a business or undertaking (PCBU) to ensure, so far as is reasonably practicable, that workers and others aren't exposed to health risks from the work. That includes biological hazards such as mosquito-borne disease. The primary duty of care applies to all work, including outdoor and field work.

Safe Work Australia has published guidance on Japanese encephalitis for PCBUs, under the model WHS laws. It makes three points that apply to your whole crew:

• Eliminating the risk is often not practicable where the work is in an area where the virus is present. In that case, you must minimise the risk as far as is reasonably practicable.
• You must inform workers about the risks and symptoms, and train them in the controls.
• Vaccination should be considered as one part of a range of controls, not as a replacement for them.

Check your state regulator's latest guidance too, as states differ in how they present it.

How to reduce exposure at work

Use a mix of controls, starting with the ones that remove the risk at source:

• Remove breeding sites. Empty containers, buckets, tyres, tarpaulins and gutters that hold water. Fix leaking taps and pipes, and cover water tanks.
• Manage wastewater and standing water. Ponded water from wash-down, drainage works or pump-outs can breed mosquitoes quickly. Drain it or treat it where you can.
• Offer vaccination. Advise workers to talk to their doctor about the JE vaccine if they work outdoors in an affected area. Keep a record of who was offered it, and who took it up.
• Provide repellent. Supply a repellent that's registered for use in Australia, and show workers how to apply it. Reapply as the label says, especially after sweating or swimming.
• Dress for cover. Long sleeves and long trousers in light colours, and clothing treated with permethrin where your plan allows.
• Plan timing. Where you can, schedule the most exposed work for times of lower biting activity, such as the middle of the day or after sunset. Note that some species bite at dusk and dawn, so check locally.
• Train the crew. Cover the diseases, the symptoms, how to use the controls, and what to do if someone gets sick.
• Monitor health. Ask workers to report bites with symptoms, and treat them promptly. Keep a confidential record of illness reports.

Use these controls in combination. Repellent on its own doesn't protect a crew working next to a pond.

Build it into your WHS system

Mosquito-borne disease is a hazard you can plan for. A few documents cover most of it:

• Safety management plan: Says who is responsible for each control, and when each one happens.
• Safe operating procedure: Step-by-step instructions for outdoor and livestock work, including the repellent and clothing rules.
• Waste and water management: Stops containers, wastewater and drainage becoming breeding sites near the work.
• Emergency response: Covers what to do when a worker becomes unwell, including first aid, who to call and how to get them to a doctor or hospital.
• Pest control: Use a qualified pest controller where mosquito numbers near work sites are high.

The Mosquito-Borne Disease Safety Plan sets out the program, and the Mosquito-Borne Disease SOP gives crews the step-by-step method. For general outdoor work, the Outdoor Work SOP covers the wider exposure issues.

Outdoor crews face other seasonal risks too. Read about heat stress management and the wider rural and agricultural health and safety issues.

Common questions

Is Japanese encephalitis notifiable? Yes. JE is nationally notifiable in humans and animals, so suspected cases should be reported to the public health unit in your state. The status of other mosquito-borne diseases varies between states, so check with your state health department.

Does a worker need a doctor's clearance before outdoor work? Not usually. What you need is a documented risk assessment, the right controls and a worker who knows the symptoms. A doctor can advise on the vaccine if a worker is at high risk.

Can we rely on repellent alone? No. Repellent is one control. Removing breeding sites, planning the work, and training and monitoring the crew all matter as much.

What should a crew do if a worker gets sick? The worker should stop work, get medical attention promptly and tell the doctor about the mosquito exposure. Your emergency procedure should name who to contact, and the supervisor should record the incident.

This is general information, not legal advice. Check the current law with your WHS regulator.