Health authorities are investigating more than 30 cases of botulism in babies linked to ByHeart infant formula since August, but there are parents who claim their children contracted the same disease months before the outbreak and are also demanding answers.
California confirmed this Friday that six babies who consumed the formula were treated for botulism between November 2024 and June 2025, up to nine months before the current outbreak, which has affected at least 31 minors in 15 states.
At that time “there was not enough evidence to immediately suspect a common origin,” the state Department of Public Health stated in a statement. And now “we cannot link any cases before August 1 to the current outbreak,” he added.
Parents of at least five babies say the children were treated for the rare and potentially lethal disease after consuming ByHeart formula in late 2024 and early 2025, according to reports shared with by Bill Marler, a Seattle food safety attorney representing the families.
Amy Mazziotti, 43, of Burbank, California, says her son Hank, then 5 months old, became ill and was treated for botulism in March, weeks after he started taking bottles of ByHeart formula.
Katie Connolly, 37, of Lafayette, California, says her daughter, then 8 months old, was hospitalized in April and treated for botulism after being fed ByHeart formula in hopes of helping her sleep.
For months, neither mother had any idea of the origin of the infections. These diseases in babies are usually caused by spores that spread in the environment or by contaminated honey.
But ByHeart announced a nationwide recall of all its products on Nov. 11 due to rising cases of infant botulism. That’s when Mazziotti said he thought, “This can’t be a coincidence.”
ByHeart confirmed this week that lab testing of unopened formulas found some were contaminated with the type of bacteria that causes infant botulism.
Attorney Bill Marler said at least three other cases before the outbreak involved babies who were fed ByHeart formula and then treated for botulism, according to their families. One consumed it in December 2024. The other two became ill later in the spring of 2025, Marler said.
The Centers for Disease Control and Prevention (CDC) said it is aware of reports of previous cases, adding that its efforts are focused however on explaining the unusual spike in the dozens of infections recorded since August 1.
“That doesn’t mean they’re not necessarily part of this,” said Jennifer Cope, the CDC doctor leading the investigation, “just that now we’re focusing on this big surge.”
Because time has passed and parents of babies who got sick earlier may not have recorded product lot numbers or saved empty cans of formula, it will be harder to definitively link them to the outbreak, he added.
Connolly says she feels her daughter has been forgotten: “I want to know why the cases that started in August led to an investigation but the ones that started in March did not.”
Cope and other health officials said the strong signal linking ByHeart to infant botulism cases only became evident in recent weeks.
Before this outbreak, no powdered infant formula had tested positive for the type of bacteria that causes botulism, according to California authorities. The number of cases also remained within the expected range. A test of an open can of formula taken by a sick baby in the spring did not detect the bacteria.
Beginning in August and continuing through October, however, more cases were found on the East Coast linked to a type of toxin rarely detected in the region, according to health officials. More cases were detected in younger babies and more linked to ByHeart, which accounts for less than 1% of infant formula sold in the US.
Earlier this November, after a sample from a can of ByHeart formula given to a sick baby tested positive, local authorities alerted the CDC, the Food and Drug Administration (FDA), and the public.
Fewer than 200 cases of infant botulism are typically reported each year in the United States. The disease occurs when babies ingest spores that germinate in the intestine and produce a toxin. The bacteria that cause the disease are ubiquitous in the environment, including soil and water, so their origin is often unknown.
The California Childhood Botulism Treatment and Prevention Program monitors reports of botulism and controls the distribution of the only treatment, an intravenous medication called BabyBIG.
Food safety experts say the CDC should count the earlier cases as part of the outbreak if the babies consumed ByHeart formula and were treated for botulism. “Absolutely yes, they should be included,” said Frank Yiannas, former FDA deputy commissioner for food policy and response, “why not include them?”
Sandra Eskin, executive director of STOP Foodborne Illness, an advocacy group, agreed: “This outbreak is traumatic for parents,” she said. “Perhaps they fed their newborns a product they assumed was safe. And now they are facing hospitalization and serious illness in their babies.”
Connolly and Mazziotti said their babies are improving but still have side effects. Botulism causes symptoms that include constipation, poor diet, and weakness in the head and limbs, among others.
After months of uncertainty about the possible cause of the infection, Connolly said he “became completely obsessed” with the connection to the ByHeart formula. Now, she just wants answers: “We deserve to know the data that helps us understand how our babies got sick.”
