# Epidemiology, serovar distribution and spatiotemporal patterns of Salmonella foodborne infections in Liaoning Province, China, 2014–2024: an analysis of sentinel surveillance data

## TL;DR

This study analyzes Salmonella infections in Liaoning Province, China, from 2014 to 2024, identifying trends, seasonal patterns, and high-risk areas to guide prevention efforts.

## Contribution

The study presents one of the longest provincial-level spatiotemporal analyses of salmonellosis in China using sentinel surveillance data.

## Key findings

- Salmonella positivity rates showed a significant upward trend from 2014 to 2024.
- Chaoyang City was identified as a consistent hotspot for Salmonella infections.
- Young children and summer months were key risk factors for salmonellosis.

## Abstract

Using long-term data from hospital-based sentinel (active) surveillance of foodborne diseases in Liaoning Province from 2014 to 2024, we examined temporal trends, seasonality, the serovar spectrum, and city-level spatiotemporal distribution of salmonellosis to inform optimization of surveillance and targeted prevention and control. This study provides one of the longest provincial-level sentinel-based spatiotemporal analyses of salmonellosis in China.

Laboratory-confirmed infections with Salmonella enterica reported by sentinel hospitals in Liaoning Province were extracted from the National Foodborne Disease Surveillance System. The Mann–Kendall test was used to evaluate monotonic trends in annual positivity rates. Monthly seasonal indices were calculated to describe seasonality. At the city level, a first-order queen contiguity spatial weight matrix was constructed to perform global and local Moran’s I analyses, with LISA results adjusted using the Benjamini–Hochberg false discovery rate (FDR) procedure. Spatiotemporal clusters were identified using SaTScan with a discrete Poisson model.

From 2014 to 2024, 38,810 cases were tested and 346 were positive for S. enterica, yielding an overall positivity rate of 0.89%. The positivity rate showed a significant, gradual upward trend (z = 2.49, p < 0.05). A unimodal seasonal pattern was observed, with high-risk months from June to August and a peak in July. Young children (particularly one-year-olds and children cared for at home) accounted for the largest proportion of detected cases. The predominant serovars were S. enterica serovar Enteritidis and S. enterica serovar Typhimurium. Global spatial autocorrelation was not significant; however, local analyses indicated that Chaoyang City remained a stable hotspot after FDR correction. SaTScan identified a Class I (most likely) spatiotemporal cluster centered on Chaoyang City for each predominant serovar (both p < 0.001).

Sentinel surveillance in Liaoning Province suggests a year-by-year increase in the detection level of Salmonella, with summer–early autumn and young children representing key risk windows. Chaoyang City consistently showed a relatively high burden in both local spatial and spatiotemporal analyses. These findings provide evidence for targeted surveillance optimization and risk-based intervention strategies in high-risk seasons, populations, and geographic areas.