A Public Health Alerts report today describes a US multistate outbreak of infant botulism tied to powdered infant formula, identifying a clear link between illness in dozens of infants and exposure to a specific formula product.

Public Health Alerts, a new collaboration between NEJM Evidence and CIDRAP, fills a gap in reliable data, offering expert-reviewed reports that translate frontline observations into actionable public health evidence. An NEJM Evidence editorial  explains the initiative further.

As detailed in today’s report, the investigation, led by California Department of Public Health investigators in collaboration with federal officials and other state health departments, identified 51 suspected or confirmed cases of infant botulism across 19 states from March 2022 to December 2025. All affected infants required hospitalization, but no deaths were reported.

Infant botulism is a rare but potentially life-threatening illness that occurs when spores of Clostridium botulinum colonize an infant’s intestine and produce a powerful neurotoxin, leading to muscle weakness and paralysis. Cases typically occur sporadically, and outbreaks are extremely uncommon. “Treatment is based on clinical diagnosis and should not be delayed for laboratory testing,” the authors of the report write.

In late 2025, clinicians noted an unusual cluster of infant botulism cases with a shared exposure to ByHeart powdered infant formula, which launched sales of its baby formula in March 2022. 

Lab testing detected botulinum neurotoxin type A and C botulinum type A in an opened container of the formula associated with one infant. Whole-genome sequencing showed genetic matches between bacteria isolated from infant stool samples and powdered formula products, strengthening evidence of a common source.

Treatment is based on clinical diagnosis and should not be delayed for laboratory testing.

The investigators also identified an atypical geographic pattern of toxin types, including rare type A cases in parts of the country where type B disease is usually dominant—another signal that prompted federal and state agencies to treat the situation as a multistate outbreak.

In response, the manufacturer initiated recalls in November 2025, ultimately expanding them to include all of its powdered infant formula products. Federal and state agencies continue to monitor for additional cases and to test ingredients and finished products to better understand how contamination occurred.

The authors emphasize that infant botulism remains rare, and that powdered infant formula is generally safe. They note, however, that this outbreak underscores the importance of rapid surveillance, laboratory capacity, and coordination across public health agencies to identify uncommon but serious risks.