The contrary short-term influence of heatwaves on Salmonellosis and Campylobacteriosis in Singapore - A national time-series analysis.

BACKGROUND

Salmonellosis and Campylobacteriosis are driven by climate variability and are among the most important causes of foodborne disease globally. Studies have largely reported positive associations between ambient air temperature and these diseases. However, those investigating how heatwaves influence these bacterial infections are few and inconsistent. I examined the short-term influence of heatwaves on these bacterial infections in the tropical city-state of Singapore.

METHODS

All national reports of Salmonellosis and Campylobacteriosis in Singapore were analysed in negative binomial regression models on a weekly timescale for their present and lagged associations with 2-day (2D-HW) and 3-day (3D-HW) heatwave events, absolute humidity and cumulative rainfall. Adjustments were made for long-term trend, seasonality, public holidays and population changes.

RESULTS

21,699 Salmonellosis and 6217 Campylobacteriosis reports from 2012 to 2024 were included. Each 2D-HW in the present and previous 6 weeks was associated with a cumulative 9.9 % (RR: 1.099, 95 % CI: 1.007 to 1.198) increase in Salmonellosis reports and a 13.0 % (RR: 0.870, 95 % CI: 0.776 to 0.975) decrease in Campylobacteriosis reports. For 3D-HWs, the direction of effect on both diseases remained consistent while the strength of association was slightly larger. Absolute humidity and cumulative rainfall were positively and negatively associated with Salmonellosis reports respectively but were not associated with Campylobacteriosis reports. Both diseases exhibited cyclical but opposite within-year patterns with different amplitudes.

CONCLUSION

This study confirms the short-term, independent contrary influence of heatwaves on Salmonellosis and Campylobacteriosis reports in Singapore as well as the potential impact of climate change on these diseases in the tropics. Health authorities can time intervention and personal hygiene advocacy measures according to anticipated heatwaves, cyclical disease variations and weather variations (the latter only for Salmonellosis) to increase their effectiveness.