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Medscape
20-05-2025
- Health
- Medscape
Flooding Triggers Major Melioidosis Outbreak in Australia
Australia has recorded its highest number of cases of the tropical bacterial infection melioidosis, which is thought to have been triggered by major rainfall and flooding. The outbreak has placed pressure on already strained hospitals in the area. The northeastern state of Queensland has recorded an unprecedented 215 cases of melioidosis so far this year compared with 59 cases over a similar period in 2024 and 46 cases in 2023. The state also recorded 31 deaths. 'We've had about four times more [cases] in Cairns and the hinterland area compared to the year-to-date average, and about six times more here in Townsville than the year-to-date average,' Jeff Warner, PhD, a microbiologist at the Australian Institute of Tropical Health and Medicine at James Cook University in Townsville, told Medscape Medical News. Both cities border the Great Barrier Reef. Townsville experienced massive floods in January and February caused by record-breaking rainfall, which is likely to have contributed to the surge in infections. Cairns has also experienced its wettest March on record. 'On top of what was already probably a spreader event back from Cyclone Jasper flooding, there's now been this additional significant weather event this year with a lot of water and a lot of flooding,' said Aileen Traves, MD, a general practitioner in Cairns. 'That obviously has made a huge difference to seeing the numbers really spike.' Aileen Traves, MD The increase in cases has put pressure on hospitals in the area, Traves told Medscape Medical News . 'There have been some additional pressures, like on intensive care here, because some of the people are so sick that they're actually ending up in the ICU.' 'Great Imitator' Melioidosis is caused by the bacterium Burkholderia pseudomallei , which is found in soil and water. The disease is endemic in tropical regions around the world, including northern Australia, and outbreaks are commonly tied to major rainfall events such as the monsoon. The infection can present as pneumonia, skin infections, or septicemia and has a mortality rate that ranges from around 10% in Australia to as high as 40% in Thailand. 'Clinically, it's one of the great imitators, along with tuberculosis and syphilis,' said Steven Donohue, MD, director of the Townsville Public Health Unit in Queensland. 'In other words, it can present in very different ways,' It can also remain latent or subclinical for a long period, potentially even decades. This feature led to its being labeled the 'Vietnamese time bomb' by US military personnel who were infected during their service in the Vietnam war. Steven Donohue, MD Those most vulnerable to severe infection tend to be older individuals with preexisting comorbidities, such as diabetes and kidney disease, and those with impaired immune systems. But one unusual feature of this latest outbreak is the number of younger, otherwise healthy individuals — particularly those working on building sites — presenting with the infection. 'They're often young, fit, and male, but they're working in conditions where they are being exposed potentially to the bacteria in their job,' Traves said. Potential Routes of Exposure How patients get exposed to and infected with B pseudomallei is still uncertain, Warner said. Bore water has been implicated as a source of infection through ingestion, as has subcutaneous inoculation via cuts or abrasions. Another possible source is inhalation. 'It's almost certainly true that it is aerosolized during the extreme weather.' Given that the organism usually resides in the soil, soil disturbance from development may be contributing to some of the clusters. 'The hypothesis up in Cairns is that the Bruce Highway extension being pushed through just south of Cairns has disrupted the environment to such an extent as to release B pseudomallei from layers of soil that weren't [normally exposed] to people,' he said. Another theory is that the cleanup from flooding in Townsville has exposed more people to the bacterium than usual. 'People are often having to clean up after floods or heavy rain in the wet, and often people are doing this with bare feet,' Donohue said. That cleanup process also sometimes includes the use of pressure hoses, which can aerosolize the water and soil and increase the likelihood of inhalation by people who are 'not necessarily wearing a mask or boots or gloves or all of the stuff they should,' he noted. Another factor could be the demographics of Australians in the area, Donohue said. 'We've got an aging population with a high rate of chronic diseases and also human movement into new suburbs and new settlements, so a lot of changes in behavior, a lot of changes in the environment.' Australia has experienced numerous extreme flooding events in recent years, particularly along the eastern coast, that have been attributed to climate change. This latest outbreak highlights the human health risks for climate change, Traves said. 'People don't always think about the associations with human health and planetary health, but I think this is a classic example.'
The Guardian
05-03-2025
- Health
- The Guardian
What is melioidosis and why do cases spike after flooding and heavy rainfall?
After major floods in north Queensland at the start of this year, 119 cases of the bacterial disease melioidosis were reported – more than three times the number of cases reported in the same period in 2024. Of these cases, 106 were from the areas around Cairns and Townsville. Sixteen people have died so far. So what is the potentially fatal disease, why are we seeing a spike in cases and what could it mean for people in the aftermath of Tropical Cyclone Alfred? Melioidosis is a rare but potentially fatal bacterial disease which occurs when people have significant contact with contaminated water or soil. Associate Professor Jeffrey Warner, a microbiology researcher from the Australian Institute of Tropical Health and Medicine at James Cook University, describes melioidosis as an 'opportunistic infection' preying on people with pre-existing health conditions such as diabetes and kidney problems as well as those who take immune-suppressing medicines. Heavy consumers of alcohol are more at risk, while people in good health are generally not susceptible to serious illness. Warner says melioidosis is a 'great mimicker' of other infections, commonly presenting as a severe chest infection with symptoms of cough, fevers and chills. But it can also affect the skin and internal organs. This mimicry can be dangerous, Warner warns, as the disease is very aggressive and resistant to most antibiotics used to treat standard infections. So rapid identification of melioidosis is critical to ensure correct 'top shelf' antimicrobial treatment. If untreated, pneumonia and sepsis can develop. Melioidosis can be fatal in up to 20% of treated cases, but Warner says people often die with the organism (from complications such as renal failure) not from it. Melioidosis is caused by the bacterial species Burkholderia pseudomallei which are found in the soil and water of tropical regions and considered endemic in Queensland and the Northern Territory. The bacteria is usually located deep in the soil but can be freed by environmental disruption, particularly floods and rainfall. It is most likely to occur in muddy soils. Infection can then occur when the bacterial cells enter susceptible people's bodies through cuts, sores, breathing it in or drinking dirty water. According to a spokesperson for Queensland Health, there have been 119 cases including 16 deaths due to melioidosis in 2025, as of 5 March. Warner says the number of cases in such a brief period is unprecedented but not surprising, because extreme weather is known to cause more cases. Given the number of cases, the rate of fatalities is within the expected rate of 5-10%, he says. 'Even when people present in well resourced hospitals, the disease can be fatal.' Because many older Australians come to Queensland to retire, they often have a higher prevalence of comorbidities, such as diabetes, that are associated with increased incidence of disease and fatality rates, he says. The disease is spread through environmental exposure – it does not usually spread between people or animals. The bacterial species is spread through the environment by rainfall, runoff water or potentially winds. 'Humans can influence its moving around by disrupting the environment … its growing health burden is at the intersection of changing climate, environment and land use,' Warner says. The bacteria typically prefers soils in the tropics, but there is evidence when climate and environmental change moves the bacteria to a non-tropical environment, it can persist, Warner says. Warner says Tropical Cyclone Alfred, expected to hit Queensland's south-east coast, could bring a spike in a number of infections associated with floods and rainfall generally, but the vast majority won't be melioidosis. Since 2013, cases of melioidosis outside north Queensland have only been in the single digits, Warner says. In 2024 there were 10 cases for whole year in the south of the state, so there is a 'little bit of evidence that meliodosis may be on the uptick but it's nowhere near as significant as up in the north'. People affected by the cyclone in the state's south-east could be more significantly affected by mosquito-borne infections, skin lesions caused by other fungi and bacteria in the environment or gastro if sewerage systems don't work, he says. However, it is possible the bacteria which causes melioidosis could travel through aerosolisation. People could potentially breathe it in when particles are carried in the air due to rains and winds during cyclonic events, he says. A spokesperson for Queensland Health encouraged Queenslanders to take precautions including wearing waterproof boots and protective gloves during cleanup following flooding events and always avoid contact with flood water if they have any broken skin or wounds.
