Flood: Disease risk heightened for weak and vulnerable

Widespread heavy rain and flooding is causing concern among health authorities due to the risk of diarrhoeal and bacterial diseases, leptospirosis, and potentially deadly viruses from mozzies.

Of the 42 cases of mosquito-borne Japanese encephalitis virus (JEV) in Australia since January 2021, seven people have died.

Dr Cameron Webb said mozzies are the most dangerous animal on the planet, with around 500,000 people dying each year because of a mosquito bite.

"Hundreds of millions of people get infected with a mosquito borne disease every year" because of the viruses and pathogens they transmit, he said.

NSW Health Pathology and The University of Sydney mosquito expert said Australia was free of many mosquito-borne diseases such as malaria and dengue fever, but JEV and Ross River virus were transmitted in Australia.

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JEV is transmitted through the bite of an infected mosquito and is mostly active in western regions of NSW, Victoria, parts of South Australia and Queensland.

Widespread flooding has exacerbated the risk of catching the virus.

"It's about trying to avoid mosquito bites as much as possible, there's no treatment for these mosquito-borne diseases," Dr Webb said.

While a vaccine for JEV is available, Dr Webb urged people to wear long pants, a long sleeve top and covered shoes when outside, and to use topical insect repellents that have diethyltoluamide (also called DEET), picaridin, or oil of lemon eucalyptus in them.

Don't leave water sources sitting in your yard, ensure pet bowls or birdbaths are flushed regularly and your rainwater tank is screened.

Flooded sewerage and drinking water systems increase the risk of diarrhoeal and bacterial diseases such as salmonella, according to experts.

The risks are present even after floodwaters subside, with some bacteria able to survive in the remaining moist environment.

"If people are working directly in floodwater that's been contaminated by human or animal sewerage you're at risk of contracting any of the nasty microorganisms that lurk in poo," Professor Philip Weinstein said.

The University of Adelaide school of public health expert said people in flooded communities should assume water had been contaminated.

"It'd be pretty impossible for it not to be contaminated, even if there's no human sewage involved, there's always going to be animal poo involved that washes in from farms and wildlife," he said.

Contaminated water is most risky for the elderly, people with compromised immunity, and those on immunosuppressant medication.

"If they get a diarrhoeal disease they're going to take longer to recover and the disease will be more serious," Professor Weinstein said.

Contaminated water can cause serious illness in some people, but the risk of lethal disease is less in Australia, Professor Weinstein said .

"If this was happening in a developing country you'd have cholera around and that's a lot more serious and can kill people, but we don't have cholera here," he said.

The advice is that if you have an extended period of flu-like symptoms such as fatigue, headache and temperature, see your doctor.

Always wear gumboots and gloves when cleaning up after a flood.

The risk of leptospirosis, which is spread by the urine of rats, had also increased due to large amounts of rubbish and debris in some areas.

The bacterial disease can be fatal and some people go on to develop severe disease such as kidney failure, jaundice, bleeding, respiratory complications and meningitis.

Most people who get JEV do not have symptoms.

Some people may get symptoms such as:

People with a severe infection (one in every 250 people) may get symptoms such as:

If you get any of these symptoms contact a doctor right away, or in an emergency call triple-0 or visit your nearest emergency department.

Symptoms include joint pain, fever and rash. Most people feel better within a few weeks, but sometimes it can take a few months.

There is no cure for Ross River virus, but pain relief medicines can help control your symptoms.