California probing baby botulism cases prior to current outbreak

Anna Edney, Bloomberg News on Nov 22, 2025

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The California Department of Public Health is investigating six additional cases of botulism in the state in infants who were given ByHeart formula before the start of the current outbreak in August, a department spokesperson told Bloomberg.

Those babies became ill between November 2024 and June 2025, said Brian Micek, a CDPH spokesperson. The department hasn’t linked the cases to the babies’ consumption of ByHeart.

ByHeart recalled two batches of its formula Nov. 8 and expanded the recall Nov. 11 to all of its product. As of Nov. 19, U.S. health officials had linked 31 cases of confirmed or suspected infant botulism to ByHeart consumption in 15 states dating back to August. All babies have been hospitalized and treated. No deaths have been reported.

There wasn’t enough evidence in early 2025 to suspect a common cause among cases. Clostridium botulinum produces spores that can be found widely in the environment including in soil and water sources, according to the World Health Organization.

“Prior to this outbreak investigation, no powdered infant formula had tested positive for Clostridium botulinum in the United States,” Micek said. “Additionally, the number of cases in general were within expected case numbers based on previous year’s trends, and disease presentation wasn’t consistent with an outbreak.”

In California, CDPH tested an open can of ByHeart in the spring that was fed to a baby who had confirmed botulism and the container tested negative, Micek said. The U.S. Food and Drug Administration has said that detection of the bacteria that causes botulism is complex, “and a negative test result does not rule out the presence of the bacteria in the product.”

CDPH provides the only treatment for infant botulism, called BabyBIG. Through its surveillance work associated with the drug, CDPH officials started noticing in August that some East Coast cases were “testing positive for a toxin type rarely detected in this region of the country,” Micek said.

“ByHeart usage was becoming more prevalent amongst cases and CDPH elevated these signals to CDC and FDA,” Micek said. “When another opened can of ByHeart consumed by a late October case in California tested positive, we were able to share those findings with CDC, FDA and the public.”

CDPH deployed its BabyBIG treatment to 107 infants around the country from Aug. 1 to Nov. 19, Micek said. This included cases of confirmed botulism and some who are awaiting final test results. As of Nov. 10, the U.S. Centers for Disease Control and Prevention said 84 infants had received BabyBIG.

The CDC reported 181 cases of infant botulism in 2021.