Testing by the U.S. Food and Drug Administration found evidence Friday that powdered whole milk used in ByHeart infant formula may be the source of a botulism outbreak that sickened 51 babies in 19 states beginning in December 2023, according to federal health officials. The FDA detected the dangerous bacteria in samples of the milk powder and found that the contamination matched samples collected from sick infants and from unopened ByHeart formula cans.
The findings point toward the supply chain as a potential source of the contamination, though the investigation continues. The discovery may help ByHeart identify how the bacteria entered its products, raising questions about industry testing standards and company responsibility.
Investigation Points to Contaminated Milk Powder
The FDA’s findings, announced Friday, marked a significant step toward identifying how the botulism bacteria entered ByHeart’s products. Laboratory testing detected the dangerous organism in two separate samples and confirmed that the contamination in the milk powder matched bacteria found in unopened formula cans and in samples collected from sickened infants.
“The findings suggest that we are significantly closer to determining the root cause of the contamination,” ByHeart officials said in a statement.
Neither the FDA nor ByHeart disclosed the name of the milk supplier. The FDA said there is no indication that the broader infant formula supply is affected.
Scope and Scale of the Outbreak
The botulism outbreak was first identified in November after officials with California’s infant botulism treatment program detected a surge in cases among babies who consumed ByHeart formula. The company initially recalled two product lots in late 2023, but expanded the recall to include all of its products days later.
Federal health officials subsequently said they could not rule out contamination of all ByHeart products manufactured since the company’s launch in March 2022. A testing report released by the company in November showed that six of 36 formula samples from three different lots contained the botulism-causing bacteria.
The CDC reported that no new cases in the outbreak have been identified since mid-December.
Regulatory Gaps and Company Liability
Illnesses caused by botulism bacteria in infant formula are rare, and the size and scope of the ByHeart outbreak is unprecedented. Some formula manufacturers test raw materials and finished products for contamination evidence, but the practice is not federally mandated.
Sarah Sorscher, director of regulatory affairs for the Center for Science in the Public Interest, said such testing should become a requirement. “Some formula companies do test raw materials and finished formula for evidence of the contamination, but such testing should be required,” she said. “FDA has not announced a plan to do testing, and that’s what we really want to see them do.”
Even if contamination originated with a milk supplier, ByHeart remains fully responsible for the harm caused by its product, according to legal experts representing families of sickened infants.
Bill Marler, a Seattle food safety lawyer representing more than 30 families whose babies fell ill, said the company’s potential ability to identify a contamination source does not absolve it of responsibility. “Just because they are able to point the finger at dried powder as the ingredient that may have been contaminated, it doesn’t take any of the legal or moral responsibility away from ByHeart,” he said.
About ByHeart
ByHeart, based in New York, held approximately 1% of the U.S. infant formula market before the outbreak. The company previously sold about 200,000 cans of formula each month. The product was marketed as an alternative close to human breast milk, made with organic, grass-fed whole milk.
Parents who chose ByHeart said they were drawn to the formula’s health marketing and premium ingredients, though the product cost approximately $42 per can—significantly more than mass-market infant formula alternatives.