Outbreak Investigation of Infant Botulism: Infant Formula
News Source: FDA
The FDA and CDC, in collaboration with the California Department of Public Health (CDPH), Infant Botulism Treatment and Prevention Program (IBTPP), and other state and local partners, investigated a multistate outbreak of infant botulism. Epidemiologic and laboratory analyses indicated that ByHeart Whole Nutrition infant formula is the source of this multistate outbreak of infant botulism.
As of February 26, 2026, CDC declares the outbreak over. During recent weeks, public health officials at state and local health departments, IBTPP, and CDC reviewed the medical records of the 51 infants who were initially included in the investigation and used additional criteria to further describe the cases. Since December 10, 2025, no new cases were added, and 3 previously reported cases from 3 states were ultimately diagnosed with other illnesses and excluded from the case count. As of February 26, 2026, the investigation includes 28 cases of confirmed infant botulism and 20 cases of probable infant botulism. Refer to CDC’s Food Safety Alert for definitions of confirmed and probable cases.
As of February 26, 2026, two isolates from one lot of organic whole milk powder, collected and analyzed by FDA, have been shown by whole genome sequencing (WGS) analysis to match a cluster of isolates reported by FDA on January 23, 2026. These two new isolates were collected by FDA at Dairy Farmers of America, the processor for Organic West Milk, which supplies ByHeart. This cluster now also includes:
- one closed powdered infant formula sample (tested by ByHeart),
- one closed powdered infant formula sample (tested by the New York State Department of Health, Wadsworth Laboratory),
- one clinical isolate,
- three isolates from one lot of organic whole milk powder (tested by ByHeart).
Additionally, WGS analysis of clinical isolates has shown that two recently analyzed clinical isolates collected and analyzed by CDPH match clusters of isolates from product samples.
One clinical isolate matches a cluster that now includes:
- three clinical isolates, and
- an open powdered infant formula sample (tested by CDPH and previously reported as confirmed positive on November 18, 2025)
The second recently analyzed clinical isolate matches a cluster that now includes:
- one clinical isolate,
- four isolates from one lot of powdered infant formula (tested by ByHeart and previously reported in FDA’s January 23, 2026, update) (This lot was reported by one patient), and
- one sample of base mix used to make powdered infant formula (tested by ByHeart)
The detection of Clostridium botulinum in infant formula, or ingredients, is complex. To date, WGS analysis has identified 17 different strains of this bacterium in samples from patients, finished products, and ingredients. While these sample results add to the available evidence needed to investigate the root cause of this outbreak, due to the complexities of Clostridium botulinum and limited scientific evidence currently available, FDA has not yet determined a root cause(s). Additional sample analysis and research is being conducted and is necessary to inform possible conclusions about this outbreak.
This outbreak is no longer ongoing, and FDA is transitioning from its initial response activities, managed by FDA’s Coordinated Outbreak Response, Evaluation & Prevention (CORE+EP) which focused on containing the event so that no additional illnesses occurred. The agency is now focused on post-incident response actions and activities, which may include additional surveillance, as well as prevention and compliance activities.
FDA will continue investigating the root cause(s) and future updates will be reported on FDA’s Actions to Respond to Clostridium botulinum Illnesses Associated with Consumption of Powdered Infant Formula, the webpage for specific information on FDA’s ongoing efforts to ensure the safety of powdered infant formula, including general information about formula safety.
