Seven dead by deadly ‘mud bug’
Thomas Jeffries explains what there is to know about an outbreak of melioidosis in flood-ravaged north Queensland.
Seven people have died from melioidosis as north Queensland faces the aftermath of record-breaking floods.
Dozens of cases have been reported in the state in recent weeks, which experts have described as unprecedented.
So, what is melioidosis, and why are we seeing a spike in cases now?
How do people get infected?
Melioidosis is caused by the bacterium Burkholderia pseudomallei, a bug that normally lives harmlessly in soil and freshwater. But it can be dangerous when it infects humans or animals.
B. pseudomallei – sometimes called the “mud bug” – enters the body through cuts or scratches. It can also be breathed in and enter the lungs via small airborne water droplets, or by drinking affected water.
Symptoms usually develop within one to four weeks after a person has been infected. The disease can cause either local infections, such as chronic skin ulcers, or, more commonly, a lung infection which can lead to pneumonia.
Symptoms of the infection include fever, headache, trouble breathing, chest and muscle pain. In rare cases, the disease can enter the bloodstream and cause septicaemia.
Treatment involves receiving intravenous antibiotics in hospital for several weeks followed by up to six months of oral antibiotics.
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The impact of floodwater on communities and public health can be destructive - devastation we're seeing unfold across North Queensland. Melioidosis can lurk in contaminated water, mud and soil, putting flood-affected communities at risk. Our thoughts are with all families affected by the floods.
— AMA Queensland (@amaqueensland.bsky.social) 14 February 2025 at 12:11
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How common is it?
Diagnosis is usually conducted using a specialist bacterial culture. This is where a sample isolated from the patient is grown in a petri dish to identify the bacteria, which can take several days.
Globally, about 165,000 cases of melioidosis are reported annually, and 89,000 deaths. The majority of cases occur in South-East Asia, particularly Thailand.
Because similar symptoms can be caused by so many other diseases, melioidosis is commonly misidentified, meaning reported case numbers are probably far lower than the actual tally of infections.
Also, cases often occur in remote communities and resource-poor settings, which can mean they’re less likely to be diagnosed.
The disease is thought to be endemic to northern Australia. It usually infects about 0.6 per 100,000 people annually in Queensland, which would be equivalent to about 30 people.
In the Northern Territory, about 17 people per 100,000 are infected annually, which would be equivalent to about 42 cases. However, this data is several years old.
In Australia, melioidosis is often treated before fatalities occur. The mortality rate has been estimated at less than 10 per cent.
More people die from the disease in lower-resource countries with poorer diagnostic capabilities and hospital facilities. In Thailand, the mortality rate is estimated to be about 40 per cent.
Who is at risk?
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Anyone can get melioidosis, but certain people are at higher risk. This includes people with diabetes, liver and kidney disease, cancer, or other conditions that might compromise the patient’s immune system.
In Australia, the disease is also significantly more common in First Nations people than among non-Indigenous Australians.
Once infected, people who are Indigenous, older or have chronic health conditions are at higher risk of poorer outcomes.
In the current outbreak in Queensland, at least three of the victims so far have been elderly.
February 2025 is officially the wettest month on record for some north Queensland towns. Image: Jamie Hervey
What’s causing the current outbreak?
Recent cases in north Queensland have been identified mainly around Townsville and Cairns.
Cairns and Hinterland Hospital and Health Service have recorded at least 41 cases since January 1, while more than 20 cases have been reported in Townsville in February.
This is most likely related to increased rainfall and flooding in and around these areas.
B. pseudomallei lives in soil and mud and comes to the surface during periods of high rainfall. So recent heavy rain and flooding in north Queensland has likely increased the risk of melioidosis.
In the Northern Territory, 28 cases have been reported since the start of the rainy season last October. However, this is lower than recent seasons.
How can you protect yourself?
If you’re in an affected region, you can protect yourself by limiting exposure to mud and water, and using appropriate personal protective equipment such as gloves and boots if spending time in muddy areas. Cover any open wounds and wear a respirator if you’re working closely with water.
Monitor for symptoms and see a doctor if you feel unwell.
Several vaccines are in development for melioidosis, and experts have recently called for it to be recognised as a neglected tropical disease by the World Health Organisation.
Particularly seeing as increasing extreme weather events due to climate change may make melioidosis more common, hopefully we’ll see an increase in research into and awareness of this disease in the years ahead.
Thomas Jeffries, Senior Lecturer in Microbiology, Western Sydney University.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
