A total of 37 infants have now been hospitalized amid an outbreak of infant botulism, a type of severe illness caused by botulinum toxin, federal health officials say.
Cases of infants with "suspected or confirmed" infant botulism have expanded to two more states, for a total of 17 states, the Centers for Disease Control and Prevention and the Food and Drug Administration said in updated advisories published Wednesday.
The total includes six new cases, up from the 31 included in the FDA's and CDC's previous updates on Nov. 20.
The outbreak now spans Arizona, California, Idaho, Illinois, Kentucky, Massachusetts, Maine, Michigan, Minnesota, North Carolina, New Jersey, Oregon, Pennsylvania, Rhode Island, Texas, Washington and Wisconsin, according to the CDC.
The FDA advisory stated that for the 36 cases with available onset information, illnesses started on dates ranging from Aug. 9, 2025, to Nov. 19, 2025.
"All 37 infants were hospitalized," the advisory stated.
Of the 35 infants with age and sex information available, ages ranged from 16 to 264 days, and 15 are female, the FDA added.
According to the FDA, no deaths have been reported to date.
The infants who fell ill were all fed "various lots" of ByHeart Whole Nutrition powdered infant formula, the FDA said.
"Laboratory confirmation for some cases is ongoing," the agency said.
The multistate outbreak investigation is being carried out by the FDA and CDC, in collaboration with the California Department of Public Health Infant Botulism Treatment and Prevention Program and other state and local health authorities, the FDA advisory stated.
The agencies' investigation into the outbreak " is ongoing to determine the point of contamination," the advisory said.
ByHeart first announced a voluntary recall of two batches of its Whole Nutrition Infant Formula on Nov. 8, "following notification from the [FDA] of a broader ongoing investigation into a recent outbreak of infant botulism."
On Nov. 11, the company said it was expanding its earlier recall to include all batches of its ByHeart Whole Nutrition Infant Formula cans and Anywhere Pack single-serve sticks nationwide.
ByHeart said in a Nov. 19 update shared on its website that recent testing showed some samples of ByHeart formula contained the bacteria Clostridium botulinum, which can cause botulism.
"We tested 36 samples from three lots and, as shared on November 19th, we received positive test results for Clostridium botulinum Type A in five of the 36 samples across all three lots. Based on these results, we cannot rule out the risk that all ByHeart formula across all product lots may have been contaminated," the company said in its latest statement.
"We want to reaffirm the critical direction for parents and caregivers to stop using ByHeart formula immediately," the company added in part. "We continue to strongly recommend monitoring for symptoms of infant botulism and to contact a medical professional immediately if your child develops symptoms."
ByHeart president and co-founder Mia Funt previously told ABC News in a statement that "the safety and well‑being of every infant who uses our formula is, and always will be, our highest priority."
Clostridium botulinum bacteria can appear in food and produce the botulinum toxin that can result in botulism.
Botulism is a rare but serious illness. According to the CDC, the botulinum toxin can attack the nerves, leading to difficulty breathing, muscle weakness and paralysis, visual disturbances, trouble swallowing, speech issues and even death.
Infant botulism occurs when a baby swallows Clostridium botulinum spores, which can then grow in the gut and produce the botulinum toxin, the agency states.
According to the Department of Agriculture's Food Safety and Inspection Service, infant botulism can affect children under 12 months of age, "but most commonly those under 2 months of age." It can occur after they eat foods such as honey that "contains spores of C. botulinum that germinate, colonize, and produce neurotoxin in the infant's intestinal tract."
"For this reason, the U.S. Food and Drug Administration, the Centers for Disease Control and Prevention, and the American Academy of Pediatrics recommend that honey not be given to children under 1 year of age," the agency states. "Also, fruits and vegetables should be washed before being fed to infants."
Symptoms of infant botulism can include poor feeding, constipation, pupils that are slow to react to light, drooping eyelids, fewer facial expressions than usual, low muscle tone or a weaker-than-normal cry.
"Seek immediate medical care if your infant has consumed ByHeart Whole Nutrition Infant Formula and has any of these symptoms: poor feeding; loss of head control; difficulty swallowing; decreased facial expression," the CDC states.
ByHeart has advised anyone with recalled ByHeart infant formula cans to stop using the product and dispose of it, and to seek emergent medical care for any infant that may be exhibiting any symptoms related to infant botulism.
As of Nov. 24, ByHeart is also offering a full refund for all products purchased on its website on or after Aug. 1, 2025, a change from the company's previous policy.
"This refund approach is guided by the most complete data available from FDA identifying the first infant in the outbreak on August 9, 2025, despite the initial notification to ByHeart on November 7, 2025," the company said in its most recent update.
Parents can contact the company via phone at 866-201-9069 and visit the company's website for refund process instructions.
