Contamination link unites infant-botulism outbreaks in US powdered formula cases

Federal health officials reveal a common source of contamination connecting two separate infant-botulism outbreaks linked to powdered formula, raising urgent questions over supply chain oversight and safety measures in the US dairy industry.

Federal health officials now say two separate infant-botulism outbreaks tied to powdered formula sold in the United States shared a common source of contamination, after closing the Nara Organics investigation on 27 August 2026 with four confirmed cases and linking one sick infant genetically to patient and product samples from the much larger ByHeart outbreak. The Food and Drug Administration said the Nara lots fed to those infants were made with milk supplied by Organic West Milk and spray-dried by Dairy Farmers of America, the same upstream suppliers identified in the ByHeart inquiry, although the agency says it still cannot tell whether contamination happened before drying or during that process. (fda.gov)

That later development has sharpened the significance of the ByHeart case, which the Centers for Disease Control and Prevention closed on 26 February 2026 with 48 infants in 17 states, including 28 confirmed and 20 probable cases. All 48 were hospitalised and treated with BabyBIG, and no deaths were reported. The FDA described ByHeart in its July 13, 2026 industry letter as the first botulism outbreak definitively tied to infant formula in the United States since infant botulism was recognised as a distinct illness nearly 50 years ago. (cdc.gov)

The first warning signs were strikingly out of proportion to ByHeart’s footprint in the market. CDC data published during the emergency response showed that, of 36 infants treated with BabyBIG between 1 August and 10 November 2025 who had any exposure to powdered formula, 15 had consumed ByHeart, even though the brand accounted for an estimated 1% of US formula sales. CDC says it was alerted on 7 November 2025 and, together with the FDA, urged ByHeart that evening to act; a two-lot recall followed on 8 November and widened to all ByHeart formula on 11 November. AAP News reported that families were told to stop using the product at once and save containers for possible testing, while Contemporary Pediatrics, citing The Associated Press, said ByHeart’s chief medical officer Devon Kuehn had put the company’s sales at about 200,000 cans a month through outlets including Whole Foods, Walmart, Target and Albertsons. AAP News also quoted paediatrician Steven Abrams saying the recall was not expected to threaten national formula supply because ByHeart was a small player. (cdc.gov)

As the evidence accumulated, the company’s early assurances became harder to sustain. On 11 November 2025, AAP News reported that ByHeart said no unopened cans had tested positive, even though California officials had already found contamination in an opened household sample. By late January 2026, the New York State Department of Health’s Wadsworth Center said it had become the first laboratory to isolate Clostridium botulinum type A from an unopened container of powdered infant formula, and that genetic analysis tied the suspect dry milk powder to finished ByHeart formula. Before that, ByHeart had already acknowledged it could not rule out wider contamination after an independent testing firm found C. botulinum type A in five of 36 samples drawn from three lots. (publications.aap.org)

The handling of the recall also drew sharp criticism. The FDA said on 20 November 2025 that recalled ByHeart formula was still turning up on shop shelves around the country, a problem AAP News also highlighted, though by 10 December the agency said it had not received further shelf reports since 26 November. FoodNavigator said the episode exposed weaknesses both in recall execution and in the company’s public messaging. Marion Nestle, the New York University nutrition scholar, told the publication that parents “have every right to expect the formula to be safe”. FoodNavigator also noted that this was ByHeart’s second recall in three years; the company had already recalled five batches in December 2022 over possible Cronobacter sakazakii contamination, and the FDA issued it a warning letter in August 2023 over unresolved concerns about process controls and corrective action. (publications.aap.org)

The scope of the outbreak changed repeatedly as investigators looked further back. On 10 December 2025, CDC said it had identified 10 earlier illnesses, dating from December 2023 through July 2025, that were also linked to ByHeart, taking the running total at that stage to 51 infants in 19 states. Jennifer Cope, chief of CDC’s Enteric Diseases Epidemiology Branch, said at the time: “While we typically expect to see 150-180 individual cases of infant botulism annually, an outbreak of infant botulism is unprecedented.” But the final review cut the tally back to 48 after three infants first included in the investigation were later found to have other illnesses. (cdc.gov)

What regulators have not yet done is announce a single, definitive root cause. What they have said is that inspections at ByHeart’s own facilities did not uncover any additional plant factor that could explain the outbreak, while the investigation did identify Clostridium botulinum in a powdered milk ingredient and produced whole-genome sequencing matches between one lot of organic whole milk powder, a clinical sample and a positive formula sample. The agency’s focus has therefore shifted upstream, towards ingredients and production environments. That scrutiny deepened when the FDA disclosed that Organic West Milk had originally provided an incomplete customer list during the 2025 inquiry and failed to reveal that its milk also reached firms making Nara Organics formula. (fda.gov)

The consequences have spread well beyond one brand. In its July 2026 letter to the infant-formula trade, the FDA pointed not only to ByHeart and Nara but also to a separate contamination episode involving arachidonic acid oil that was linked to nearly 150 suspected and confirmed cereulide intoxication cases across 10 countries. The message from regulators was that infant-formula safety cannot stop at the factory gate: supplier oversight has to extend across the whole chain. The FDA has since moved into post-outbreak surveillance, including powdered-milk sampling, while continuing to investigate where the botulism hazard entered the dairy stream. What remains unresolved is the precise point of contamination; what is no longer in doubt, according to the CDC and FDA, is that contaminated formula made infants sick in both outbreaks. (fda.gov)