Outbreak of <i>Salmonella</i> Typhimurium Infections Linked to Commercially Distributed Raw Milk — California and Four Other States, September 2023–March 2024

Unpasteurized (raw) milk has been linked to foodborne illness outbreaks caused by Escherichia coli bacteria and certain species of Brucella, Campylobacter, Cryptosporidium, and Salmonella. In October 2023, the County of San Diego Health and Human Services Agency notified the California Department of Public Health (CDPH) of eight cases of salmonellosis in persons who reported consuming brand A raw milk, produced exclusively by dairy farm A. A total of 171 outbreak-associated Salmonella Typhimurium cases were identified through review of standardized salmonellosis case report forms and a search of PulseNet, CDC's national molecular subtyping network for enteric disease surveillance, followed by administration of a dairy-focused supplementary questionnaire. Most cases (98%) were identified in California; one case each was identified in four other states. Among the 171 cases, 120 (70%) cases and 18 (82%) of the cases requiring hospitalization were among children and adolescents aged <18 years. Among 159 patients confirmed to be infected with the outbreak strain, 55 (70%) of those with exposure data consumed brand A raw milk or heavy cream. Four of 40 samples collected from dairy farm A, retail stores, and patients' homes, including raw milk and raw milk cheese aged for 60 days, tested positive for the outbreak strain of S. Typhimurium by whole-genome sequencing. Dairy farm A voluntarily recalled raw milk and raw heavy cream 1 week after the initial outbreak identification. Commercially distributed raw dairy products have the potential to cause large and widespread infectious disease outbreaks. Public health authorities should continue to raise awareness of the risks associated with consuming raw dairy products, especially by persons at increased risk for severe disease from enteric pathogens, including children.