ByHeart Formula Linked to Botulism Cases Months Before Official Outbreak

In March, Amy Mazziotti's five-month-old son Hank fell ill after drinking ByHeart formula. Weeks of uncertainty followed—no clear diagnosis, no obvious cause. Then in November, ByHeart recalled all its products nationwide after health officials linked the brand to a surge of infant botulism cases. The moment Mazziotti heard the news, the pieces clicked into place. "This cannot be a coincidence," she thought.

But there was a problem with that clarity: Hank's illness had occurred eight months before the outbreak was officially recognized. He was not alone. California public health officials confirmed late last week that six babies in the state had been treated for botulism after consuming ByHeart formula between November 2024 and June 2025—months before the current outbreak sickened at least 31 infants across 15 states. Katie Connolly's eight-month-old daughter, M.C., was hospitalized in April after being fed ByHeart formula. At the time, neither mother knew what had made their children sick. Botulism in infants typically traces back to environmental spores or contaminated honey, not formula. The connection seemed invisible.

When ByHeart recalled its products on November 11, laboratory tests of unopened formula revealed the answer: some samples contained the bacterium responsible for infant botulism. The company's confirmation came this week. Food safety lawyer Bill Marler, representing affected families, says at least three additional cases predating the August outbreak involved babies who consumed ByHeart and were treated for botulism—one in December 2024, two more in spring. Yet health officials maintain they cannot definitively connect these earlier illnesses to the current outbreak.

The reasoning is straightforward but unsatisfying to parents. California health officials stated there was "not enough evidence to immediately suspect a common source" when those six cases appeared. Before this outbreak, no powdered infant formula in the U.S. had tested positive for botulism-causing bacteria. The number of cases fell within expected ranges. A test of an open can of formula fed to a sick baby in spring did not detect the bacterium. Only when cases began clustering in August and October—concentrated on the East Coast, involving a toxin type rarely seen in that region, and disproportionately affecting very young infants—did the pattern become visible. The signal only strengthened when a sample from a can of ByHeart formula fed to a sick infant tested positive.

Dr. Jennifer Cope, the CDC scientist leading the investigation, acknowledges the agency is aware of reports of earlier illnesses. But federal efforts remain focused on the documented surge since August 1. "That doesn't mean that they're not necessarily part of this," Cope said. "It's just that right now, we're focusing on this large increase." She added that time and missing documentation make it harder to definitively link earlier cases. Parents who did not record lot numbers or retain empty formula cans cannot easily prove the connection now.

Connolly finds this reasoning hollow. "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?" she asked. Outside experts agree. Frank Yiannas, former deputy commissioner for food policy at the FDA, said earlier cases should absolutely be counted as part of the outbreak if babies consumed ByHeart and were treated for botulism. "Why wouldn't they be included?" he asked. Sandra Eskin, chief executive of STOP Foodborne Illness, framed the stakes plainly: "This outbreak is traumatic for parents. 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."

Botulism causes constipation, poor feeding, weakness in the head and limbs, and other complications. Both Mazziotti and Connolly say their children are improving, though lingering effects remain. After months of searching for answers, Connolly became what she describes as "completely obsessed" with linking ByHeart to her daughter's illness. Now she wants the data that explains how her baby got sick. The question hanging over this outbreak is whether the investigation's focus on the recent surge has left earlier cases—and the families who lived through them—in shadow.