Weather conditions associated with climate change are exacerbating the spread of foodborne pathogens Salmonella and Campylobacter, suggest recent studies by researchers at the University of Surrey’s School of Veterinary Medicine.

The studies were led by Gianni Lo Iacono, Ph.D., Senior Lecturer of Biostatistics and Epidemiology in Surrey University’s School of Veterinary Medicine.

Weather Conditions Aiding the Spread of Salmonella

According to the University of Surrey, Salmonella infections are responsible for nearly one-third of foodborne illnesses in Europe.

A recent study published in the Journal of Infection used a novel statistical model to estimate salmonellosis incidence based on 14 different weather factors. These factors were determined through analysis of UK Health Security Agency (UKHSA) data for confirmed cases of Salmonella infection in England and Wales between 2000 and 2016, compared against weather data from the UK Met Office.

Looking at the combined effect of various weather conditions on salmonellosis incidence, the researchers determined key factors contributing to an increase in Salmonella infection:

• Warmer temperatures (above 10 °C)
• Relative humidity (dewpoint of 7–10 °C)
• Longer day lengths (12–15 hours).

Other weather factors, such as air pressure, wind speed, temperature amplitude, and sunshine duration, showed limited or no association with the number of salmonellosis cases.

The model was also used independently in the Netherlands with similar results, showing its promise for providing insight into Salmonella incidence. To strengthen their conclusions, the researchers would like the model to be tested in social and climatic conditions largely different from the UK.

Similar Findings for the Effect of Weather on Campylobacteriosis Incidence

The Salmonella weather study builds upon previous work by University of Surrey researchers, published in PLOS Computational Biology, which showed that weather conditions associated with climate change may also worsen the spread of campylobacteriosis. According to the World Health Organization (WHO), Campylobacter infections are the most common cause of human bacterial gastroenteritis in the world.

Similar to their study of the impacts of weather on Salmonella spread, the researchers analyzed data from approximately one million campylobacteriosis cases confirmed by UKHSA over a 20-year period, and compared it against weather data provided by the UK Met Office.

The researchers found that campylobacteriosis cases were consistent at temperatures below 8 °C, but noted a significant increase in infections (approximately one case per million) for every 5-degree rise in temperatures. High campylobacteriosis incidence was also seen at 75–80 percent humidity. Additionally, long days (more than 10 hours) were associated with a rise in Campylobacter infections. Rainfall and wind speed were not strongly linked to campylobacteriosis spread.