2023–2024 Raw Milk Salmonella Outbreak Overview
On July 24, 2025, the California Department of Public Health (CDPH) and cooperating local agencies released the final Morbidity and Mortality Weekly Report (MMWR) on one of the largest raw milk–linked Salmonella Typhimurium outbreaks in recent US history. Previously, only fragmentary press releases and social media notices hinted at the scope. The outbreak, spanning September 2023 to March 2024, affected at least 171 people across five states, with young children disproportionately impacted.
Background and Initial Alerts
On October 20, 2023, San Diego County health officials issued a press release identifying nine cases of salmonellosis linked to raw (unpasteurized) milk and cream from Raw Farm LLC. By October 25, the combined case count in San Diego and neighboring Orange County had risen to 19, prompting a recall of all Raw Farm fluid dairy products. Despite these early alerts, CDPH never issued a consolidated press release; instead, it posted three terse tweets between October and December 2023 with minimal outbreak details.
Final Investigation Findings
- Total cases: 171 (159 confirmed via whole genome sequencing [WGS], 12 probable)
- Geographic spread: 167 in California (35 local health jurisdictions), plus individual cases in New Mexico, Pennsylvania, Texas, and Washington
- Age distribution: 120 (70%) cases among children and teens; 67 (39%) under age 5
- Hospitalizations: 22 (82% were minors); no fatalities reported
“I was just candidly shocked that there was an outbreak of 170 plus people, because it had not been reported—at all.”
—Bill Marler, foodborne illness attorney
Genomic Surveillance and Traceability Tech
Public health labs utilized Illumina MiSeq-based WGS and core genome multi-locus sequence typing (cgMLST) via the CDC’s PulseNet network to link clinical isolates to raw milk and cheese samples. Analyses showed fewer than 10 single-nucleotide polymorphisms (SNPs) among outbreak strains, confirming a point-source contamination. Raw Farm’s on-site lab used ISO 17025-accredited methods, but results trailed behind federal sequencing pipelines.
On-Farm Biosecurity and Production Controls
Raw Farm’s pasteurization avoidance runs counter to standard Hazard Analysis and Critical Control Points (HACCP) protocols. Key vulnerabilities included:
- Shared milking equipment without routine sanitizer validation (e.g., 200 ppm free chlorine residual)
- Lack of rapid ATP bioluminescence testing on teat surfaces
- Infrequent environmental swabbing for Salmonella spp. across holding pens
Regulatory Gaps and Public Communication Protocols
Federal law prohibits interstate raw milk sales, yet two out-of-state cases reported consuming Raw Farm products via private networks. This loophole illustrates the difficulty of enforcing FDA Milk Safety Branch guidelines across state lines. Furthermore, the delayed MMWR publication—amid a reported slowdown in CDC outputs—hampered real-time risk communication.
Expert Opinions and Legal Actions
Attorney Bill Marler, representing ~24 plaintiffs, secured interim and final state reports only after threatening subpoenas. Marler argues that prompt disclosure could have mitigated further cases. Raw Farm founder Mark McAfee disputes the outbreak scale, attributing positives to a single removed cow and dismissing genomic links. Public health experts, however, maintain that robust genomic clustering and epidemiological interviews conclusively tied Raw Farm products to the multi-state outbreak.
Deep Analysis: Supply Chain Vulnerabilities
Direct-to-consumer raw milk sales often leverage agile e-commerce platforms and decentralized distribution nodes, complicating cold chain monitoring. IoT sensors measuring time–temperature integrals (TTIs) and blockchain-based batch tracking are emerging solutions to improve transparency.
Conclusions and Recommendations
To prevent future large-scale outbreaks, agencies and producers should:
- Implement mandatory on-farm WGS screening every 30 days
- Adopt digital traceability systems with QR-coded batch passports
- Enhance public messaging through unified press releases and real-time dashboards
Latest Developments
In June 2025, the FDA announced a pilot raw dairy pathogen surveillance program in five states, integrating rapid nanopore sequencing and machine-learning–based anomaly detection. Early results suggest this could reduce outbreak detection time by 50%.