In late 2025, babies who were fed organic ByHeart Whole Nutrition infant formula began to fall ill with botulism across the U.S. Less than one year later, in June 2026, a new infant botulism outbreak has emerged across several states, this time involving Nara Organics Whole Milk Infant Formula.

Until now, C. botulinum has not been considered to be a hazard reasonably likely to occur in powdered infant formula manufacturing. But with two high-profile outbreaks of infant botulism linked to seemingly similar products—whole milk powder-based formulas marketed as using organic, “clean” ingredients, sold under smaller, privately owned brands—one might begin to wonder whether these incidents are due to industrywide blind spots, or perhaps could have been prevented through stronger regulatory oversight.

The important question on everyone’s mind is: what is the way forward to prevent future formula-associated infant botulism outbreaks?

C. botulism in Powdered Infant Formula: A ‘New’ Hazard?

Although sporadic cases of infant botulism are known to occur due to a number of causes, the ByHeart outbreak brought the issue of C. botulism contamination in powdered infant formula into the spotlight. The new Nara outbreak further underlines the importance of reconsidering C. botulinum as a hazard in formula production processes.

Brian Ronholm, Director of Food Policy at Consumer Reports, explained to Food Safety Magazine that, historically, there have been approximately 150 infant botulism cases per year in the U.S., but the numbers have recently increased. The latest data from the U.S. Centers for Disease Control and Prevention (CDC) show 181 confirmed infant botulism cases in 2021.

In the ByHeart outbreak alone, 48 infants were sickened in 17 states. The earliest onset of illness was December 2023, but the majority of cases occurred between March and November 2025. As of June 19, 2026, three infants in three states have fallen ill as part of the Nara Organics outbreak between April and May of this year.

Both outbreaks were first flagged by the California Department of Public Health’s Infant Botulism Treatment and Prevention Program (CDPH’s IBTPP), which operates the only source of infant botulism treatment worldwide, BabyBIG.

New Evidence Suggests Gold-Standard C. botulinum Testing is Insufficient

On June 14, 2026, a ByHeart-commissioned study was published in Frontiers in Microbiology suggesting that sulfite-reducing clostridia (SRC) enumeration, which is recommended as a general indicator of spore contamination by the International Commission on Microbiological Specifications for Foods (ICMSF), may not be enough to ensure powdered infant formula is free of C. botulinum.

This study was conducted as a part of ByHeart’s investigation into the 2025 outbreak linked to its product. A third-party laboratory, IEH Laboratories and Consulting Group was engaged to screen, detect, and characterize C. botulinum from finished products, using a tiered analytical approach combining anaerobic enrichment, molecular screening, culture confirmation, and genomic analysis.

The authors concluded that “indicator-based screening (such as SRC enumeration) even if it had been in place before the [ByHeart] outbreak, would not have prevented its occurrence.”

At present, SRC enumeration is upheld by Nara Organics—as well as by competitors that also produce organic formulas marketed as wholesome and clean—as evidence of the companies going above and beyond to ensure food safety. For example, on its website, formula maker Bobbie said it uses SRC testing as an “extra layer of safety” implemented in the wake of the ByHeart outbreak, calling it an “early warning system” for C. botulinum. Additionally, in a company email, Little Spoon said it goes “further than required” by using SRC testing, which is not required by the U.S. Food and Drug Administration (FDA), holding itself to “a standard 10 times stricter than international guidance.”

Unfortunately, SRC testing was also in place at Nara Organics before babies began falling ill with botulism. According to the company website, Nara tests to ten times the international best practice recommended by ICMSF, which set a maximum level of less than 100 colony forming units per gram (CFU/g). Nara had set its specification at less than 10 CFU/g, and went as far as to test each batch of formula for SRC at three stages (i.e., raw ingredients, formula powder during production, and finished packaged product).

What About the Ingredients and Processes?

Both ByHeart and Nara Organics formulas are organic, whole milk powder-based products. The companies have marketed their formulas as using only high-quality, wholesome ingredients and as being held to more rigorous safety standards than those required in the U.S.

While ByHeart is manufactured in-house at the company’s own domestic production facilities, Nara Organics is manufactured by a German company, Milchwerke Mittelelbe GmbH (Elb-Milch), a subsidiary of the Krüger Group. According to Food Safety News, the manufacturer uses milk from 100 contract farmers who supply Milchwerke Mittelelbe with more than one million liters of milk every day.

On the other hand, ByHeart’s powdered milk used in its formulas was supplied by Organic West Milk and processed by Dairy Farmers of America (DFA). The company’s and FDA’s root cause investigations identified C. botulinum in a powdered milk ingredient, and FDA inspections at DFA revealed C. botulinum in two samples of the same lot of organic whole milk powder, which matched a clinical isolate and a positive infant formula finished product sample.

Despite surface-level similarities between the two companies, however, the root causes as to why C. botulinum ended up in their finished formula products is more difficult to elucidate. Still to this day, FDA has been unable to pinpoint the root cause of contamination of the powdered milk ingredient used in ByHeart formula.

Larry Keener, CFS, PA, an internationally regarded microbiologist and process authority who has extensive experience working with clostridia, told Food Safety Magazine that looking at the ingredients lists for Nara Organics’ and ByHeart’s formulas raises several questions and cannot provide clear answers.

However, speaking generally about C. botulinum in infant formula manufacturing, the processing of the oils used—that is, whether they are cold-pressed or heated (deodorized)—could make a difference in the potential spore load arriving with those ingredients. Additionally, it is also possible for the steps in a manufacturing process to be selective for thermally resistant spores.

When a Hazard Becomes Reasonably Foreseeable: Specific Preventive Controls Needed

In the ByHeart-commissioned study finding SRC enumeration to be insufficient, the authors wrote, “Manufacturers [should] recognize C. botulinum as a hazard reasonably likely to occur in certain ingredients, necessitating the design and implementation of specific preventative controls.”

However, according to Mr. Ronholm, “testing for C. botulinum can be tricky and often requires secure labs (Biosafety Level 3), which dramatically reduces the number of places that can test for it. The expanded scope of the ByHeart outbreak resulted in more scrutiny of this issue.”

Despite the practical challenges of integrating C. botulinum-specific testing into production workflows, there is a consensus among stakeholders that the pathogen must now be treated more seriously as a hazard.

Mr. Ronholm shared his thoughts. “FDA should declare C. botulinum as an adulterant in infant formula and require testing for it. Infant formula manufacturers should be testing and monitoring for C. botulinum in both the food production environment—such as food contact surfaces—and for environmental testing in the plants.”

Frank Yiannas, M.P.H., former FDA Deputy Commissioner of Food Policy and Response who has also held food safety leadership roles at Walmart and the Walt Disney Company, told Food Safety Magazine, “While some have suggested that we need additional C. botulinum prevalence surveys to determine whether it is a hazard in the powdered infant formula supply chain, the available evidence—including recent findings and previous work—already indicates that it is.” He added, “It is time for all parties involved—both the private and public sectors—to recognize C. botulinum as a reasonably foreseeable hazard. While it may represent a low-frequency, high-severity risk, the consequences are simply too great to ignore. The focus now should be to urgently identify root causes, strengthen science-based preventive controls, and supply chain oversight to better protect our most vulnerable consumers—infants.”

Legislators are currently attempting to strengthen infant formula safety through an active bill, the Infant Formula Safety Modernization Act, which would, among other directives, mandate FDA to require manufacturers to test formula for C. botulinum. The bill was introduced by Representative Rosa DeLauro (D-CT), who said in a statement about the Nara Organics outbreak, “This is not an isolated incident—it is a concerning pattern that begs the question; are we doing enough to ensure the safety of infant formula in this country? Pass the Infant Formula Safety Modernization Act now.”