Temporal trends and source attribution of animal-contact related human nontyphoidal Salmonella enterica outbreaks across the United States, 2009–2022

PURPOSE: Previous studies have assessed nontyphoidal Salmonella enterica (NTS) outbreaks associated with animal contact over short periods or single exposures. This study longitudinally evaluates the incidence, temporal trends, and all relevant exposure sources of NTS outbreaks attributed to animal contact in the United States (US) from 2009 to 2022. METHODS: Surveillance data on animal-contact-related NTS single-state outbreaks in the US, reported to the Centers for Disease Control and Prevention through the National Outbreak Reporting System between 2009 and 2022, were analyzed. First, yearly and state-specific NTS outbreak incidence rates (IRs) per one million population years (1 MPY) were calculated. Next, join point regression models assessed national and state-specific trends in NTS IRs over the study years. Lastly, the proportion of NTS outbreaks attributed to various animal contact sources was described. RESULTS: During the 14 years, 104 NTS outbreaks were reported (0.02 per 1 MPY). The highest outbreak IRs were observed in 2014 (0.0534 per 1 MPY), 2018 (0.0459), and 2009 (0.0389). The join point regression analysis did not identify a significant trend in the national NTS outbreak IRs; however, several states were identified with increasing and/or decreasing trends. Contact with mammals was the main exposure category (n = 37 outbreaks, 35.58 %), followed by birds (n = 31, 29.81 %) and reptiles (n = 24). CONCLUSIONS: Continued public health resources to mitigate the health burden of NTS infections are needed. Differences in state-level NTS outbreak IRs call for focused NTS prevention and control programs.