ByHeart formula may have sickened other babies months before botulism outbreak

Public health officials say six babies in California who drank ByHeart formula were treated for botulism months before the current outbreak that has sickened at least 31 babies in 15 states.

Parents said their infants were treated for the rare and potentially deadly disease after drinking ByHeart formula in late 2024 and early 2025, some nine months before the formula was recalled nationwide, according to reports shared with The Associated Press by Bill Marler, a Seattle food safety lawyer representing the families. 

Infant botulism cases in California 

What they're saying:

Amy Mazziotti, 43, of Burbank, California, said her then-5-month-old son, Hank, fell ill and was treated for botulism in March, weeks after he began drinking bottles filled with ByHeart formula.

Katie Connolly, 37, of Lafayette, California, said her daughter, M.C., then 8 months old, was hospitalized in April and treated for botulism after being fed ByHeart formula in hopes of helping the baby sleep.

For months, neither mother had any idea where the infections could have originated. Such illnesses in babies typically are caused by spores spread in the environment or by contaminated honey.

RELATED: Recalled ByHeart baby formula still on store shelves, officials find

Then ByHeart recalled all of its products nationwide on Nov. 11 in connection with growing cases of infant botulism.

As soon as she heard it was ByHeart, Mazziotti said she thought: "This cannot be a coincidence."

Why wasn’t ByHeart formula recalled sooner?

The other side:

At the time, there was "not enough evidence to immediately suspect a common source," the California Department of Public Health said in a statement.

Even now, "we cannot connect any pre-August 1 cases to the current outbreak," officials said, despite ByHeart confirming that some samples of previously unopened formula were contaminated with the type of bacteria that leads to infant botulism.

Dig deeper:

U.S. Centers for Disease Control and Prevention said federal investigators were aware of reports of earlier illnesses but that efforts are focused now on understanding the unusual surge of dozens of infections documented since Aug. 1.

"That doesn’t mean that they’re not necessarily part of this," said Dr. Jennifer Cope, a CDC scientist leading the probe. "It’s just that right now, we’re focusing on this large increase."

Before this outbreak, no powdered infant formula in the U.S. had tested positive for the type of bacteria that leads to botulism, California health officials said. The number of cases also were within an expected range. A test of a can of open formula fed to a sick baby in the spring did not detect the bacterium.

Then, beginning in August and through October, more cases were identified on the East Coast involving a type of toxin rarely detected in the region, officials said. More cases were seen in very young infants and more cases involved ByHeart formula, which accounts for less than 1 percent of infant formula sold in the U.S.

Earlier this month, after a sample from a can of ByHeart formula fed to a sick infant tested positive for the germ that leads to illness, officials notified the CDC, the U.S. Food and Drug Administration and the public.

What is infant botulism?

The backstory:

Less than 200 cases of infant botulism are reported in the U.S. each year. The disease is caused when babies ingest spores that germinate in the gut and produce a toxin. The bacterium that leads to illness is ubiquitous in the environment, including soil and water, so the source is often unknown.

Botulism causes symptoms that include constipation, poor feeding, head and limb weakness and other problems.