The aftermath of floods often leaves people without access to clean water, forcing them to use contaminated water for everyday tasks and cooking, greatly increasing the likelihood of food-borne illness. (Image credit: AFP via Getty Images)
Global warming has made it easier for bacteria and other microorganisms to contaminate food, and this subtle threat of climate change is delivering painful and sometimes life-threatening lessons to hundreds of millions of people every year. One such victim is 75-year-old Sumitra Sutar from the village of Haroli in the Indian state of Maharashtra.
Five years ago, Sutar was eating leftover rice and lentil curry, her staple diet for more than five decades. This time, her usual fare caused her to vomit “at least 15 times a day,” she recently recalled. She eventually discovered that the culprit was food-borne bacteria that produce toxins that cause vomiting, eye inflammation, and respiratory infections. Global warming has made conditions more favorable for the pathogen Bacillus cereus, which thrives in foods stored after cooking. One study found that cooking rice at home may not be enough to kill its spores.
Scientists and health officials are raising the alarm: Food supplies are becoming more vulnerable to spoilage due to an increase in extreme temperatures, floods and droughts, raising the likelihood of foodborne illnesses and outbreaks. Extreme heat can speed up food spoilage by allowing bacteria to multiply more quickly, experts say. Rising waters from severe floods can contaminate crops with sewage or other unwanted waste, while increased humidity can promote the growth of salmonella bacteria on lettuce and other foods that are eaten raw. The World Health Organization says 600 million people become ill with foodborne illnesses each year, leading to 420,000 deaths. Children under five are particularly at risk, with 125,000 children dying each year from these largely preventable diseases.
A variety of factors, including agricultural practices and global food supply chains, have made such problems much more common, and a growing body of research highlights that climate change also plays a significant role.
A review study published in the journal eBiomedicine this year found that for every 1.8 F (1 C) increase in temperature, the risk of contracting nontyphoidal Salmonella and Campylobacter — bacteria that commonly cause food poisoning — increased by 5%.
Greenhouse for microbes
Sutar's village has seen a sharp rise in temperatures over the past decade, with summer temperatures reaching 109.4 F (43 C). Many residents in the area have reported an increase in food-borne illnesses, said community health worker Padmashree Sutar, who is also Sumitra Sutar's daughter-in-law.
A review article published in the journal Climatic Change notes that higher temperatures and changing precipitation patterns are facilitating the spread of foodborne pathogens, the most common of which are Salmonella, E. coli, and Campylobacter jejuni.
“Elevated temperatures promote the growth of bacteria such as listeria, campylobacter and salmonella in perishable foods such as meat, dairy products and seafood,” said study co-author Ahmed Hamad, a lecturer in food hygiene and control at Egypt's Benha University.
A study in northwestern Mexico examined how environmental factors influence outbreaks of different types of Salmonella, responsible for many foodborne illnesses around the world. It found the highest prevalence in areas with higher temperatures of 35 to 37 °C (95 to 98.6 F) and annual rainfall of more than 1,000 mm (39.4 in).
Another paper published in Applied and Environmental Microbiology this year says that
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