Babies who drank ByHeart formula got sick months before botulism outbreak, parents say

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.

Parents of at least five babies said that their infants were treated for the rare and potentially deadly disease after drinking ByHeart formula in late 2024 and early 2025, according to reports shared with The Associated Press by Bill Marler, a Seattle food safety lawyer representing the families.

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.

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.”

ByHeart officials this week confirmed that laboratory tests of previously unopened formula found that some samples were contaminated with the type of bacteria that leads to infant botulism.

Marler said at least three other cases that predate the outbreak involved babies who drank ByHeart and were treated for botulism, according to their families. One consumed ByHeart formula in December 2024. The other two were sickened later in the spring, he said.

An official with the 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.”

Because so much time has passed and because parents of babies who got sick earlier may not have recorded lot numbers of product or kept empty cans of formula, “it will make it harder to definitively link them” to the outbreak, Cope said.

Connolly said it feels like her daughter has been forgotten.

“What I want to know is why did the cases beginning in August flag an investigation, but the cases that began in March did not?” Connolly said.

Cope and other health officials said the strong signal connecting ByHeart to infant botulism cases only became apparent in recent weeks.

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.

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.

Officials at the California Infant Botulism Treatment and Prevention Program track reports of botulism and the distribution of the only treatment for the illness, an IV medication called BabyBIG.

Outside food safety experts said the CDC should count earlier cases as part of the outbreak if babies consumed ByHeart formula and were treated for botulism.

“Absolutely, yes, they should be included,” said Frank Yiannas, former deputy commissioner for food policy and response at the U.S. Food and Drug Administration. “Why wouldn’t they be included?”

Sandra Eskin, chief executive of STOP Foodborne Illness, an advocacy group, agreed.

“This outbreak is traumatic for parents,” she said. “They may have fed their newborns and infants a product they assumed was safe. And now they’re dealing with hospitalization and serious illness of their babies.”

Connolly and Mazziotti said their babies are improving, though they still have some lingering effects. Botulism causes symptoms that include constipation, poor feeding, head and limb weakness and other problems.

After months of uncertainty about the potential cause of the infection, Connolly said she “became completely obsessed” with the link to ByHeart formula. Now, she just wants answers.

“We deserve to know the data that can help us understand how our babies got sick,” she said.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.