A nationwide infant botulism outbreak linked to ByHeart powdered formula has ended after sickening 48 babies in 17 states, according to federal health officials.
The now-closed investigation found 28 confirmed and 20 probable cases of infant botulism in babies who consumed ByHeart Whole Nutrition infant formula. Three additional suspected cases from three states were later excluded after doctors found other causes. The infants ranged in age from 16 to 264 days, and nearly half were female.
Every infant in the outbreak was hospitalized and treated with BabyBIG, an intravenous medication made from the pooled blood plasma of adults immunized against botulism. No deaths were reported, a major contrast with earlier eras when infant botulism fatality rates approached 90 percent before falling to under 1 percent with modern care.
California’s Infant Botulism Treatment and Prevention Program, the sole global supplier of BabyBIG, provides 24-hour consultation for suspected cases.
The scale of the ByHeart outbreak stands out in part because botulism tied to infant formula is exceptionally rare. Infant botulism develops when babies swallow Clostridium botulinum spores that germinate in the intestines and release a powerful toxin attacking the nervous system, causing symptoms that can advance from constipation and trouble feeding to flaccid paralysis and breathing problems.
California’s Infant Botulism Treatment and Prevention Program first detected an unusual rise in infant botulism cases among babies who had consumed ByHeart formula around August 2025 and alerted federal partners. Illness onset dates for outbreak cases stretched from Dec. 24, 2023, through Nov. 29, 2025.
ByHeart, a New York-based company that once represented about 1 percent of the U.S. infant formula market and sold roughly 200,000 cans a month, had marketed its product as offering “next-to-breast milk benefits.” Some parents whose children were later hospitalized said they chose the formula, which cost about $42 per can, because of those advertised health advantages.
The company’s recall unfolded over several days in November 2025. ByHeart first pulled two lots of its organic, whole-milk powdered formula, then expanded the recall to all infant formula products on Nov. 11, 2025. Regulators later said they could not rule out contamination in products manufactured since the brand’s March 2022 launch, prompting major retailers and online sellers nationwide to remove the product.
Although the outbreak investigation is officially closed, the search for how the bacteria entered the production chain remains unresolved. FDA investigators have not yet determined a definitive root cause but reported finding 17 different strains of the botulism-causing bacteria in samples from patients, finished formula, and ingredients. The agency said those findings “add to the available evidence needed to investigate the root cause of this outbreak,” but are not conclusive.
Previously, regulators pointed to powdered whole milk used in ByHeart’s production process as a possible contamination source. Epidemiologic and laboratory evidence showed that ByHeart Whole Nutrition infant formula was contaminated with C. botulinum and made infants sick, and California health officials confirmed C. botulinum type A in a culture from an opened can fed to one affected infant.
Health officials say the outbreak is over, but continue to urge parents not to use any remaining ByHeart formula and to wash items and surfaces that may have touched it with hot, soapy water or a dishwasher. Parents are urged to seek immediate medical care if an infant who consumed ByHeart formula shows poor feeding, difficulty swallowing, loss of head control, or decreased facial expression, and to remain alert because symptoms can take weeks to appear.