Författare: Cameron Webb Clinical Associate Professor and Principal Hosp

While some parts of southeast Queensland and northern New South Wales are still on alert for flooding, others are starting the difficult clean-up process as flood waters recede.

Stagnant water after floods provides the perfect breeding ground for mosquitoes. So as you clean up, remember to empty containers of water and other reservoirs around your house and yard such as water-filled boats, trailers and other large objects. Get rid of debris that may be collecting water too.

This year, mozzies are carrying the usual viruses we want to avoid, such as Ross River virus, but the potentially deadly Japanese encephalitis virus has also been detected in parts of New South Wales and Queensland.

Will more mozzies mean more disease?

In February 2020, floods in northern NSW boosted mosquito activity and increased cases of mosquito-borne diseases caused by Ross River and Barmah Forest viruses in subsequent months.

But while flood waters may boost mosquito numbers, outbreaks of disease don’t always follow. Hurricanes in North America have been associated with increased mosquito populations but few outbreaks of disease.

In Australia too, there are few examples of mosquito-borne disease outbreaks after cyclones – with a notable exception. After Tropical Cyclone Zoe made landfall in 1974, we had one of the one of the biggest outbreaks of Murray Valley encephalitis virus later in the year.

Warmer weather helps drive big mosquito populations, and the forecast predicts a warmer-than-normal autumn. So health authorities are on the lookout for outbreaks of disease.

Health authorities in Queensland and NSW are monitoring activity of mosquitoes and mosquito-borne pathogens.
A/Prof Cameron Webb (NSW Health Pathology)

Japanese encephalitis is already active

Somewhat dry conditions in the summer of 2024-25 have meant mosquito populations in many regions of eastern Australia have remained well below average.

But cases of Japanese encephalitis virus have been widely detected in Victoria, NSW and Queensland – in mosquitoes, piggeries and feral pigs.

Humans have also been infected. Cases are rare but the disease can be serious, with symptoms ranging from fever, headache, and vomiting through to disorientation, coma, seizure and brain swelling. One person has died of the virus this year.

Japanese encephalitis virus first arrived in southeastern Australia over the summer of 2021-2022. That followed extensive flooding across the Murray Darling Basin thanks to the arrival of La Niña. At the time, there were phenomenal numbers of mosquitoes that continued over subsequent years as the above average rainfall continued.

In the summer of 2022-23, a significant outbreak of Murray Valley encephalitis was also linked to ongoing flooding. This disease has similar symptoms to Japanese encephalitis and can also be fatal.

Read more:
Explainer: what is Murray Valley encephalitis virus?

Mosquito numbers this summer have only been a fraction of what was recorded during those seasons influenced by La Niña. The activity of Japanese encephalitis in 2024-25 has scientists scratching their heads, as it goes against the commonly held theories that greater mosquito numbers combined with increased waterbird activity (typically following flooding) drive greater transmission of viruses such as Japanese and Murray Valley encephalitis.

Fortunately, there is no evidence of these viruses along the coast of southeast Queensland through to northern NSW.

But regions where the virus has already been active, such as Darling Downs in Queensland and Moree in NSW, may see substantial rainfall as a result of ex-Tropical Cyclone Alfred.

Predicting outbreaks is incredibly difficult and relies not just on mosquito activity but also on on the dynamics of the the wildlife hosts that carry these viruses

But unpredictable mosquito-borne disease combined with extreme weather is not a good mix.

It’s unclear how much mosquito-borne diease we’ll see after ex-Tropical Cyclone Alfred.
A/Prof Cameron Webb (NSW Health Pathology)

Don’t forget about Ross River virus

While not life threatening, disease caused by Ross River virus can be severely debilitating with joint pain and fatigue lasting many weeks or months.

Thousands of cases of infection are reported across the country each year, including in urban areas of southeast Queensland and northern NSW.

Concerns about Ross River diseases were already raised with heavy rain and flooding in northern Australia this summer. Case numbers often peak at the end or summer and early autumn. So there is potential for greater activity in the coming months.

Other mosquito-borne pathogens, such as Barmah Forest virus, may also be circulating and may cause cases of mild disease but these occur far less commonly than those due to Ross River virus infection.

Protect yourself while cleaning up

If you’re out cleaning up after the storms, try to avoid mosquito bites.

Cover up with long-sleeved shirts, long pants and covered shoes for a physical barrier against mosquito bites.

Use topical insect repellents containing DEET, picaridin, or oil of lemon eucalyptus. Be sure to apply an even coat on all exposed areas of skin for the longest-lasting protection.

For those living or working in regions of Queensland, NSW and Victoria at risk of Japanese encephalitis, a safe and effective vaccine is available. Läs mer…

Wrangling head lice, and the children they infest, must be up there with the most challenging duties a parent or carer has to face.

And the job is getting harder. Commonly used chemical products aren’t working as well as they once did, meaning head lice are harder to kill.

You can still rid your children of lice – but it’s likely to take some patience and persistence.

Remind me, what are head lice? And nits?

Head lice are tiny six-legged insects that are only found in the hair on a human’s head – most commonly in the hair of primary school-aged children.

Head lice have been a constant companion for humans throughout their millions of years of evolution.

Lice love living in our hair. But they scoot down to our scalp up to a half dozen times a day to drink our blood.

Their claws are perfectly designed to scuttle up and down shafts of hair. But while they’re nimble on our hair, once they’re off, they don’t last long –they’re clumsy, uncoordinated and die quickly.

The term “nits” actually describes the eggs of head lice. They’re often the first sign of an infestation. And with one louse laying more than 100 in their month-long lifespan, there can be a lot of them.

Head lice live for around a month.
logika600/Shutterstock

Can they spread diseases?

No. Head lice are annoying and their bites may cause skin reactions. But Australian health authorities don’t consider lice a health risk. There is no evidence that head lice can spread pathogens that cause disease.

The stigma of head lice infestations can be greater than any direct health consequences for infested children.

Why do my children always pick up lice?

From child care through to primary school, it’s likely your child has had a head lice infestation at least once. One Australian study found the infestation rate in Australian classrooms ranged from no cases to 72% of children affected.

Girls are more likely to be carry head lice than boys. Long hair means it’s easier for the head lice to hitch a ride.

One study found that in some classrooms, almost three in four children had head lice.
CDC/Unsplash

Head lice don’t jump or fly, they move from head to head via direct contact.

Head lice come home with your children because they spend time in close contact with other children, hugging, playing or crowding around books or screens. Any head-to-head contact is a pathway of infections.

Rules differ slightly between states but in New South Wales and Queensland, children don’t need to be kept home from school because of head lice.

How can I keep my home free of head lice?

Keeping the house clean and tidy won’t keep head lice away. They don’t care how clean your bed sheets and towels are, or how frequently you vacuum carpets and rugs.

There may be a risk of head lice transfer on shared pillows, but even that risk is low.

There’s no need to change the child’s or other family member’s bedding when you find lice in a child’s hair. Research-based recommendations from NSW Health are that “bed linen, hats, clothing and furniture do not harbour or transmit lice or nits and that there is no benefit in washing them as a treatment option”.

I’ve used nit solution. Why isn’t it working?

A wide range of products are available at your local pharmacy to treat head lice. Australia’s Therapeutic Goods Administration assesses products to ensure that they are both safe and effective.

The problem is that most of these products are insecticides that kill the lice on contact but may not kill the eggs.

Also, if treatments aren’t completed as directed on product labels, some head lice won’t be killed.

Head lice also seem to be fighting back against the chemicals we’ve been using against them and it’s getting harder to clear children of infestations.

So how can you get rid of them?

You’ll need conditioner and a nit comb.
riopatuca/Shutterstock

Don’t expect any miracle cures but health authorities in Australia generally recommend the “conditioner and comb” or “wet comb” method. This means you physically remove the lice without the need for chemical applications.

There are three key steps:

immobilise the lice by applying hair conditioner to the child’s damp hair and leaving it there for around 20 minutes
systematically comb through the hair using a fine toothed “lice comb”. The conditioner and lice can be wiped off on paper towels or tissues. Only adult lice will be collected but don’t worry, we’ll deal with the eggs later
repeat the process twice, about a week apart, to break the life cycle of the head lice.

Repeating the process after a week allows the remaining eggs to hatch. It sounds counter-intuitive but by letting them hatch, the young lice are easier to remove than the eggs. You just need to remove them before they start laying a fresh batch of eggs and the infestation continues.

While children are much more likely to have head lice, the reality is that everyone in the household is just as likely to host a head louse or two. You don’t necessarily need everyone to have a treatment but “grown ups” should be on the lookout for lice too. Läs mer…