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  1. Outbreaks of Foodborne Illness

Post-Outbreak Response Activities: Clostridium botulinum Illnesses Associated with Consumption of Powdered Infant Formula

Infant botulism is a rare but serious illness caused by spores from a bacterium called Clostridium botulinum. These spores are naturally found in the environment including in soil and sediments (dust) and can enter manufacturing facilities and home environments from hands, shoes, and other contaminated surfaces. 

Overview of recent Clostridium botulinum illnesses and contamination of powdered infant formula

From late 2025 through early 2026, the FDA and CDC, in collaboration with the California Department of Public Health (CDPH)’s Infant Botulism Treatment and Prevention Program (IBTPP) and other state and local partners, investigated a multistate outbreak of infant botulism. In total, 48 infants became ill across 17 states. On February 26, 2026, the CDC declared the outbreak over and FDA’s inspections at the ByHeart facilities also concluded.

The FDA’s investigation revealed the firm's root cause investigations included a focus on incoming ingredients, such as powdered milk. As a part of FDA’s investigation, we inspected ByHeart's manufacturing facilities. These inspections led to the identification of Clostridium botulinum in a powdered milk ingredient. The inspections at the ByHeart facilities did not identify any additional factors that could explain the cause of this outbreak.

The FDA  also conducted an inspection at Dairy Farmers of America (the processor for Organic West Milk, which was a supplier to ByHeart). FDA and ByHeart sampled dairy ingredients from Dairy Farmers of America. Two samples from one lot of organic whole milk powder were shown by whole genome sequencing (WGS) analysis to match a clinical sample and a positive infant formula sample. The FDA's investigation into the root cause is ongoing with a focus on ingredients.  

Additional details about the outbreak can be found on the Outbreak Investigation page. 

FDA’s Ongoing Post-Response Activities

The FDA has transitioned from its initial response activities associated with the 2025 outbreak and is now focused on post-outbreak response actions and activities to help prevent future illnesses, which include:

  • Continued investigation into the root cause of the 2025 outbreak, including assessment of the supply chain and dairy-based ingredients. 
  • Surveillance sampling to better assess the presence of Clostridium botulinum in powdered milk. 
  • Efforts to understand risks associated with Clostridium botulinum and best practices for the manufacturing of powdered infant formula.
    • The FDA advocated for the Joint FAO/WHO Expert Meeting on Microbiological Risk Assessment (JEMRA) to conduct a risk assessment on spore-forming pathogens, including Clostridium botulinum and Bacillus cereus, in powdered infant formula.
    • The FDA has also supported the Codex Committee on Food Hygiene request to JEMRA to 1) update the existing risk assessment and scientific advice on Cronobacter and Salmonella in powdered infant formula and 2) provide other relevant scientific advice that would inform recommendations on strengthened control measures across infant formula production, covering all stages from primary production and packaging to the reconstitution of the product and including environmental monitoring.
  • Communications and engagement with industry, consumers, federal, state, local, and other public health partners about enhancing infant formula safety.

The FDA will continue to update this page with additional actions that occur related to FDA’s efforts to prevent future infant botulism illnesses linked to consumption of powdered infant formula.

Infant Botulism

Infant botulism is a rare but serious illness caused by toxin from a bacterium called Clostridium botulinum. Spores from this bacterium are naturally found in the environment including in soil and sediments (dust).  They can enter manufacturing facilities and home environments from hands, shoes, and other contaminated surfaces. 

Clostridium botulinum spores are generally harmless to older children and adults with mature, healthy digestive systems. However, they can pose a life-threatening risk to infants. When ingested spores begin to grow they produce toxin, which interferes with the nervous system.

There are fundamental differences between bacteria that form spores like Clostridium botulinum and those that do not, such as Cronobacter and Salmonella. These differences are crucial to understanding food safety contamination risks and assessing testing strategies.

  • Non-spore-forming bacteria (e.g., Cronobacter and Salmonella) do not form protective spores.  While dangerous, they are susceptible to pasteurization.
  • Spore-forming bacteria (e.g., Clostridium botulinum) are incredibly resilient.  They can create a protective spore that allows them to survive typical pasteurization and harsh environmental conditions for long periods. This makes the spores more difficult to eliminate from food processing environments.  
  • Spore-forming bacteria analysis and laboratory detection methods differ from traditional pathogen detection methods. They require additional time and specialized resources, which limits the number of labs with testing capacity.  The complex testing process can take two or more weeks for final results.

These two categories of bacteria present distinct contamination risks and require different prevention and testing strategies due to their vastly different survival capabilities and environmental presence. These are important considerations as the FDA considers risk reduction strategies going forward.    
 

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