California health officials say the current outbreak of infant botulism linked to ByHeart formula was preceded by several cases that began in November 2024. To date, more than 100 infants have been treated for botulism poisoning.
The California Department of Public Health (CDPH) reports that at least six cases of infant botulism were detected between November 2024 and March 2025. Before the current outbreak was announced, it was thought to have started in August this year.
There are currently 31 confirmed patients from 15 states. All infants required hospitalization, but none died. Spores that cause botulism poisoning have been found in unopened containers of ByHeart infant formula. All affected infants were fed formula, according to the US Centers for Disease Control and Prevention.
“CDPH continues to investigate, but at this time we are unable to link any cases that occurred before August 1 to the current outbreak,” a CDPH spokesperson said.
The spokesperson explained that at the beginning of 2025 there was not enough evidence to immediately suspect a common source among the six suspected cases, and that the number of cases was within the expected number of cases based on trends in previous years.
Prior to the current outbreak, no powdered infant formula tested positive for C-botulinum in the United States. CDPH reported that from Aug. 1 to Nov. 19, 107 infants nationwide were treated with BabyBIG, a treatment for infants with botulism derived from human plasma. This includes confirmed cases and infants who were being treated while awaiting test results.
CDPH developed and is the sole source of BabyBIG. The CDC and Food and Drug Administration began investigating the outbreak after officials from CDPH's Infant Botulism Treatment and Prevention Program alerted them to an increase in requests for treatment.
ByHeart initially recalled two lots of its powdered infant formula. As the investigation into the outbreak progressed, the company recalled all of its infant formulas. The FDA is warning parents and guardians that some of the recalled formulas are still on store shelves.
The infant formula was sold in other countries and warnings were issued in some of them.
Symptoms of childhood botulism poisoning include constipation, poor nutrition, loss of head control and difficulty swallowing, which can progress to difficulty breathing and respiratory arrest. Symptoms of infant botulism, which is diagnosed clinically, may develop several weeks after ingestion of formula.
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