Salmonella warning as Queensland heats up

Queensland is expected to face growing pressure on its health system as rising temperatures drive an increase in serious Salmonella infections, according to a decade-long analysis of climate and disease data.

The study was led by James Cook University PhD candidate and infectious diseases physician Dr Naveen Manchal. He said climate change, increased ambient temperatures and increasingly frequent heatwaves are expected to alter the epidemiology of various food-borne pathogens, such as Salmonella.

“We investigated the link between rising temperatures and heatwaves across Queensland and cases of Salmonella and Campylobacter that had progressed to the bloodstream, a condition known as bacteraemia,” Dr Manchal said.

He said Salmonella and Campylobacter usually cause gastroenteritis, while bacteraemia is much more serious and commonly requires hospitalisation.

Researchers analysed more than 1,000 Salmonella bacteraemia cases and 234 Campylobacter cases recorded between 2010 and 2019, comparing them with detailed weather data. They found no meaningful association between temperature and Campylobacter.

However, they identified a clear and statistically significant link between hotter weather and Salmonella bloodstream infections, particularly in Southeast Queensland and the Tropical North.

“In Southeast Queensland, each 1°C rise in mean temperature increased the risk of Salmonella bacteraemia by 8 to 20 per cent. Maximum temperatures showed a similar pattern, with the risk rising up to 16 per cent,” Dr Manchal said.

“The effect was even stronger in the Tropical North, where a 1°C increase in mean temperature was associated with an 18 per cent rise in cases, peaking at 27.2°C. When maximum temperatures climbed above 28°C, the risk jumped sharply, increasing by 11 to 105 per cent for each additional degree.”

Central Queensland showed a mild upward trend, though results were not statistically significant. Timing also varied by region, with cases peaking within a week of hotter weather in the southeast but taking around three weeks in the Tropical North.

Heatwaves added further strain.

“During extreme heat events, Salmonella bacteraemia rose by 31 per cent for every degree increase in maximum temperature,” Dr Manchal said.

The research team warned that as Queensland continues to warm, the state can expect more severe Salmonella infections requiring hospital care, longer antibiotic treatment and potentially higher mortality.

Dr Manchal said coordinated action across environmental health, food safety and climate adaptation agencies will be crucial to reducing the risks posed by a hotter climate.

The study forms part of Dr. Manchal’s PhD research supervised by Associate Professor Oyelola Adegboye, an expert in biostatistical modelling and environmental health.

Link to paper here.

Background:

Salmonella usually occurs after eating contaminated food such as undercooked poultry, eggs, meat, unpasteurised dairy, or fresh produce exposed to contaminated water. It can also spread through contact with infected animals or poor hand hygiene.