Animal contact-related nontyphoidal Salmonella enterica outbreaks in humans in the U.S. (2009-2022): serovar-specific temporal trends and associations with exposure sources and settings.

BACKGROUND

Nontyphoidal Salmonella enterica poses a public health risk. Investigating the associations between different serovars and their exposure sources and settings can guide prevention and control efforts.

METHODS

Surveillance data on animal contact-associated single-state outbreaks in the U.S., reported to the Centers for Disease Control and Prevention via the National Outbreak Reporting System (NORS) between 2009 and 2022, were analyzed. Descriptive statistics described the serovar-specific incidence rates and the distribution of exposure sources and settings. The co-occurrence patterns of serovars, exposure sources, and settings were evaluated using network analysis and multiple correspondence analysis. Serovar-specific temporal trends were assessed using locally estimated scatterplot smoothing (LOESS) and the Mann-Kendall test.

RESULTS

From 2009 to 2022, a total of 104 NTS outbreaks were reported. Salmonella Typhimurium was the most dominant serovar (n = 33; 31.73%), followed by S. I 4,[5],12:i:- (n = 15; 14.42%), and S. enteritidis (n = 10; 9.62%). Serovar Enteritidis was linked to poultry, while Typhimurium and I 4,[5],12:i:- were associated with mammals, reptiles, and agricultural settings. Among 32 serovars, only Montevideo showed a significant temporal decrease in prevalence (tau = -0.549; p-value = 0.02), while the main serovars remained stable. Network analysis revealed interconnections among serovars, exposure sources, and settings, with S. typhimurium acting as a central hub linking various animal hosts and exposure environments. Reptile-associated outbreaks were a significant subset, dominated by serovars S. Agbeni, S. Poona, S. Pomona, and S. Cotham.

CONCLUSION

The findings of this study can inform public health authorities in their efforts to reduce the burden of NTS infections. The persistence of NTS serovars across diverse animal sources and exposure settings highlights the ongoing zoonotic transmission risk at the human-animal-environment interface. A comprehensive, One Health approach to prevention and control is suggested to mitigate the health burden of NTS outbreaks.