An analysis has shown that higher temperatures lead to more Salmonella and Campylobacter infections.
Peer-reviewed epidemiological studies published between January 1990 and March 2024 were searched.
Of the 3,472 results, 44 studies were included in the systematic review, each covering more than 1 million cases of Salmonella and Campylobacter infections. In total, 22 studies examined Salmonella infection, 15 studies examined Campylobacter and seven examined both infections. Studies covered 27 countries across five continents, but most were from high-income countries.
For every 1 degree C (33.8 degree F) increase in temperature, the risk of Salmonella and Campylobacter infections increased by 5 percent.
Findings published in The Lancet journal eBioMedicine highlight the relationship between temperature and the incidence of Salmonella and Campylobacter infections.
Higher temperatures directly affect the growth and replication of pathogens, but also indirectly affect food storage, dietary habits such as consuming raw or undercooked food, and food handling during warmer weather.
Scientists say the results demonstrate the importance of implementing targeted interventions and measures, such as establishing localized early warning systems and preventive strategies that take climate variability into account.
National notifiable disease surveillance systems and regional health databases were the main data sources in most studies, and hospital data were used twice. 40 studies collected exposure data from national meteorological agencies, and the remaining four used remotely sensed and validated temperature data.
Findings of Salmonella and Campylobacter
For studies of Salmonella infections, researchers have observed a positive relationship between the annual mean temperature of the study sites and the effect estimates obtained from the continent of Oceania, compared to estimates from Asia. However, they did not find any relationship between latitude, longitude and a country’s GDP per capita.
Temperature plays a crucial role in the spread of pathogens. Salmonella exhibits optimal multiplication within a temperature range of 35 to 37 degrees C (95 to 98.6 degrees F). However, when temperatures drop below 15 degrees C (59 degrees F), spread is significantly reduced.
Campylobacter species thrive best at 30 to 42 degrees C (86 to 107.6 degrees F). There was a significant positive association between GDP per capita and the effect estimates from studies of Campylobacter infections.
Effect estimates derived from the warm summer Mediterranean climate zone showed a positive relationship with the warm summer continental climate zone. However, scientists found no correlation between effect estimates for infection studies and continent, latitude, longitude or annual average temperatures of the study sites.
Studies have identified major risk factors for infection, including consumption of chicken, contact with raw meat and having unpasteurized milk or grilled beef, all of which are affected by changes in environmental temperature.
“The existing evidence from epidemiological studies suggests that high temperatures increase the risk of intestinal infections. The link between temperature and intestinal infections varies by climatic zone, continent and income level. These findings can aid healthcare planning and inform the development of tailored preventive measures and optimization of resource allocation,” researchers said.
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