A Formula for Disaster: Infant Botulism Outbreak

 “After all, botulinum toxin is the world's most potent natural toxin—millions of times more poisonous than cyanide.”

USDA Agricultural Research Service

"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."

Sandra Eskin, chief executive, STOP Foodborne Illness

One of the reasons I chose to pursue a career in internal medicine rather than pediatrics was because nothing was more unnerving to me than being responsible for the medical care of a very sick infant. So when on November 12, 2025, there was a report of an outbreak of infant botulism—by then a total of 15 confirmed or suspected infant botulism cases in the U.S.—my sympathies quickly aligned not only with the parents but also with the healthcare providers. In this week’s Germ Gems post, I provide a brief overview of botulism as well as an update on the current infant botulism outbreak triggered by contaminated ByHeart Whole Nutrition formula.

What is botulism? Botulism is a rare and potentially fatal illness caused by botulinum toxin produced by the bacterium Clostridium botulinum. Bacterial spores which cause the disease are common in soil and water. When these spores are exposed to a low oxygen environment (anaerobic conditions) and certain temperatures, they produce the toxin. It is botulinum toxin, a neurotoxin, that causes the illness and not the bacterium itself. The three most common ways the toxin can enter the body are through contaminated food, colonization of the gut (infant botulism), and wounds.

Food-borne botulism occurs when food containing the toxin is eaten. The most common cause of food-borne botulism is improperly preserved food—improperly prepared home-canned food substances and fermented dishes without adequate salt or acidity. Symptoms can appear within 6 hours after eating but also up to 10 days thereafter. Multiple people who consume food from the same source may be infected.

Infant botulism is the most common form of the illness found in Western countries. It happens when the bacterium develops in the intestines and releases the toxin in infants during the early stages of their lives—typically in children less than one year old as protective mechanisms against the disease develop after that age. Symptoms can take up to several weeks to develop.

Wound botulism is another setting of the disease. It usually results from the contamination of a wound and occurs most often in those who inject street drugs. In this situation, spores enter a wound and, in the absence of oxygen, release the toxin.

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The disease begins with weakness in the muscles of the arms, legs and chest, blurred vision, fatigue, and trouble speaking. Vomiting, swelling of the abdomen, and diarrhea may also occur. Clinicians often think of the symptoms of botulism in terms of a classic triad: bulbar palsy (weakness of the muscles of the face, throat, and tongue due to damage to the neurons that control them), lack of fever, and a clear mental status. The diagnosis is confirmed by detecting the botulinum toxin in a patient’s serum stool or gastric fluid or by culturing C. botulinum from a stool or wound sample. But as lab results can take time, treatment is typically initiated based on the clinical diagnosis.

Botulism is treated with an anti-toxin that blocks the toxin’s action and also with supportive care. (Wound botulism requires cleaning of the wound in addition to the anti-toxin.) The anti-toxin is administered intravenously and is most effective when given early. For infants under one year old, a specific immunoglobulin is used.

In the U.S., there are roughly 150 reported cases of botulism per year with infant botulism comprising the majority of cases. There are fewer than five deaths annually. Death is caused by respiratory failure but, fortunately, in the last 50 years the proportion of patients with botulism who die has fallen from 50% to 7% due to improved supportive care.

Infant botulism. First recognized in 1976, infant botulism—also referred to as floppy baby syndrome—has been reported in all 50 states and in 26 countries on five continents. It is the most common form of botulism in the U.S.  

It occurs when a baby swallows Clostridium botulinum spores that then colonize the large intestine. The growth of the spores releases botulinum toxin which is absorbed into the bloodstream and binds to nerve endings causing paralysis by blocking the release of the neurotransmitter acetylcholine.

Infants are susceptible during the first year of life, with more than 90% of the cases occurring in infants younger than six months. At this young age, a child’s intestinal tract isn’t colonized by bacteria in their gut microbiome that compete with C. perfringens which develops at a later age. (You may not know that honey is a known reservoir of the spores and for this reason isn’t recommended for infants.)

Typical symptoms of infant botulism include constipation, lethargy, weakness, difficulty feeding, an altered cry and lack of head control. The toxin can also cause paralysis of the trunk, arms, legs and respiratory system and can possibly cause respiratory arrest.

Infant botulism is treatable with an antitoxin called BabyBIG (Botulism Immune Globulin). The antitoxin is given intravenously and works like an antidote, neutralizing the toxin circulating in the infant’s blood. It is important to begin treatment early based on clinical findings and not wait for the results of laboratory confirmatory testing. And, although it may take several weeks to months, most children fully recover.

ByHeart Whole Nutrition infant formula outbreak. ByHeart infant formula products account for roughly 1% of all infant formula sold in the U.S. The current infant botulism outbreak has been traced to contaminated ByHeart Whole Nutrition Infant Formula. On November 8, 2025, ByHeart issued an initial recall notice. On November 11, 2025, ByHeart conducted a full recall of all ByHeart Whole Nutrition Infant Formula cans and Anywhere Pack nationwide.

Illness onset in the current outbreak ranged from August 9, 2025 to November 13, 2025. According to reports from the U.S. Centers for Disease Control and Prevention and the Food and Drug Administration, by November 20, 2025, 31 cases of infant botulism in 15 states were reported. (The states are Arizona, California, Idaho, Illinois, Kentucky, Maine, Michigan, Minnesota, North Carolina, New Jersey, Oregon, Pennsylvania, Rhode Island, Texas, and Washington.) All sick infants were hospitalized and treated with BabyBIG with the aim of neutralizing botulinum toxin with these anti-toxin antibodies. To date, no deaths have been reported.

While the root cause of this outbreak is still unknown, it appears the worst is over. And I am sure we can all appreciate the relief expressed by the mother of an infant hospitalized with the disease who said, “She’s going to make a full recovery. They said we just got very lucky to catch it as early as we did and that she’s done as well as she has and that she got the medication as soon as she did.”

In all of medicine, timing is important. It can be everything…even the cure.