The California Department of Public Health (CDPH) has identified additional cases of infant botulism occurring as early as November 2024 that could potentially have an unconfirmed link to the ongoing ByHeart infant formula outbreak.

Officially, as of November 19, 2025, the outbreak comprises 31 cases of illness across 15 states, and includes illnesses that began between August 9 and November 13, 2025

A spike in infant botulism cases was first noticed by CDPH’s Infant Botulism Treatment and Prevention Program (IBTPP), which operates the only global source of infant botulism treatment worldwide.

According to CDPH, this spike has grown from the originally reported 84 cases to now include 107 cases of infant botulism, occurring between August 1, 2025 and November 19, 2025. Not all infants treated for infant botulism during this spike have confirmed exposure to ByHeart infant formula.

Typically, less than 200 cases of infant botulism are reported in the U.S. each year.

Additionally, CDPH has reported another six cases of infant botulism with exposure to ByHeart infant formula that occurred between November 2024 and June 2025. Although these cases are under investigation by CDPH, at present, any cases that occurred before August 1, 2025 have not been definitively linked to the current outbreak, said a CDPH spokesperson.

According to information provided to the Associated Press (AP) by attorney Bill Marler, who is representing several families of sickened infants who consumed ByHeart formula, parents of at least five babies said their infants were treated for botulism in late 2024 and early 2025, months ahead of the infant botulism spike noticed by CDPH.

In early 2025, CDPH explained, there was not enough evidence to suspect a common vehicle of illness, and at the time, there was not an unusual number of illnesses based on previous years’ trends.

Additionally, a U.S. Centers for Disease Control and Prevention (CDC) spokesperson told AP that federal outbreak investigation efforts are focused on the unusually large number of cases that occurred after August 1. It will be more difficult to definitively link cases that happened before August 1 to the current outbreak, due to the amount of time that has passed and it being unlikely that parents would have recorded product lot numbers or kept empty cans of formula.

The number of infant botulism cases counted by CDPH is based on the number of infants treated with BabyBig, a plasma-derived infant botulism treatment developed and provided by CDPH’s IBTPP. The sole provider of BabyBig is IBTPP.

On November 19, ByHeart Inc. announced that independent third-party testing contracted by the company had confirmed the presence of Clostridium botulinum in its product.

Earlier laboratory test results from CDPH identified the presence of C. botulinum in an open can of ByHeart infant formula that was fed to an infant with botulism. Additional testing of samples from outbreak patients are underway by several state agencies, and the U.S. Food and Drug Administration (FDA) is also collecting and analyzing samples of unopened product.

All ByHeart formula products have been recalled nationwide.

Since the outbreak has come to light, ByHeart has come under increasing scrutiny for a history of food safety failures, including FDA inspections finding mold, dead insects, and leaking roof issues at a production facility. ByHeart was also issued a warning letter by FDA in 2023 for the presence of Cronobacter sakazakii in its product.

Update, November 26, 2025: ByHeart Inc. has found Clostridium botulinum Type A in five of 36 samples across three lots. “Based on these results, we cannot rule out the risk that all ByHeart formula across all product lots may have been contaminated,” said the company.

As of November 26, the number of infant botulism cases in the associated outbreak has grown to 37 across 17 states. Additionally, FDA has released ByHeart facility inspection reports from as early as 2022 showing a history of food safety breaches.