HEATWAVES can have a major influence on the spread of disease new research by Irish scientists has found.
The study conducted by researchers at Trinity College Dublin, found that a multitude of factors related to sudden heatwaves can have a significant impact on environmentally transmitted diseases.
It also found that many existing predictive models related to the spread of disease have overlooked this factor.
“While scientists have a relatively good idea of how temperature impacts some viruses and disease-causing pathogens and parasites, they know much less about the effects of sudden heatwaves or cold snaps, or how influential variation in the duration of these events are,” the report authors explain.
Specifically, the scientists discovered that differences in heatwaves – such as how much hotter they are than normal temperatures, and how long they last – can increase or decrease disease burden by up to 13 times.
Their discovery and its implications come at a time when global climate change and related extreme weather events are impacting counties across the globe, and their findings have been published in the leading international journal PLOS Climate.
“In this study, we worked with the water flea (Daphnia magna) and a microsporidian pathogen (Ordospora colligata), which is a widely used model for environmentally transmitted diseases, to investigate the impacts of different heatwave attributes,” first author, Niamh McCartan, a PhD candidate from Trinity’s School of Natural Sciences, said this week.
“We manipulated the amplitude and duration of heatwaves across four average temperatures and four distinct time points at which the hosts were exposed to the pathogen.
“This approach gave us 64 unique heatwaves for comparison.”
The results showed that, when compared to other types of temperature variation, such as cold snaps, heatwaves alter parasite burden up to 13-fold, which drives significant variation in infection outcomes.
“A recently published study reported that 58 per cent of human pathogenic diseases have been aggravated by climate change, with temperature changes impacting host susceptibility due to altering biological properties such as how our immune systems function, as well as our behaviour,” Ms McCartan explained.
“From a bigger-picture perspective, this work underlines the need for more detailed, context-specific models to help better predict the likely impact of heatwaves and climate change on different diseases.
“We now know that amplitude, duration, baseline temperature and the point at which exposure occurs have differing effects in shaping disease outcomes, so overly simplified models may miss critical complexities.”
She explained: “For example, other researchers have suggested almost 70 per cent of Covid-19 cases in the summer of 2022 could have been avoided if there hadn’t been heatwaves around that time – imagine the difference that a better understanding of how heatwaves alter disease dynamics could have made to countless people?”
“Climate change is also causing mosquito species that carry diseases like dengue, Zika, and malaria to be increasingly found in parts of southern and central Europe, including Italy and France, areas that were previously too cool to support them.
“While Ireland has so far been less affected, the findings of our study highlight the urgent need to understand how warming and extreme weather events can alter disease dynamics more broadly.
“With all of this in mind, it’s important that future disease-specific models must account for fluctuating and extreme temperatures, not just averages.”
