The number of infant botulism cases tied to baby formula has climbed to 15. Here's what to know

Federal and state officials are investigating the outbreak, which began in mid-August. No deaths have been reported.

ByHeart, a maker of organic baby formula based in New York, recalled two lots of its Whole Nutrition Infant Formula over the weekend.

“Consumers in possession of this product should stop using it immediately,” California officials said.

Here’s what to know about the outbreak and infant botulism.

Infant botulism outbreak started in August

The outbreak has sickened babies aged 2 weeks to 5 months since mid-August. The infants were hospitalized after consuming ByHeart powdered formula, according to the U.S. Centers for Disease Control and Prevention.

ByHeart officials agreed to recall two lots of the company's Whole Nutrition Infant Formula, according to the U.S. Food and Drug Administration. They include lots 206VABP/251261P2 and 206VABP/251131P2, with best-by dates of December 2026.

California officials confirmed that a sample from an open can of ByHeart baby formula fed to an infant who fell ill contained the type of bacteria that causes the toxin linked to the outbreak. The tests to confirm contamination involve injecting mice with the cultured bacterium and then waiting up to four days to see if they get sick.

“These mice got sick really quickly,” Pan said in an interview.

ByHeart officials called for testing of unopened cans of formula from the recalled batches.

“Testing unopened cans will provide reliable evidence that will help bring clarity to families who are understandably concerned,” the company said in a statement Monday.

At least 84 babies in the U.S. have been treated for botulism since August, California officials said. That includes those confirmed to have been fed ByHeart formula.

The FDA is investigating whether any of the others are also linked to the same baby formula.

Causes of infant botulism

Infant botulism typically affects fewer than 200 babies in the U.S. each year. It is caused by a type of bacteria that produces a toxin in the large intestine. The bacterium is spread through hardy spores present in the environment that can cause serious illness, including paralysis.

Infants younger than 1 are particularly vulnerable to infection because their gut microbiomes are not developed enough to prevent the spores from germinating and producing the toxin. They can be sickened after exposure to the spores in dust, dirt or water or by eating contaminated honey.

Symptoms can take weeks to develop and can include poor feeding, loss of head control, drooping eyelids and a flat facial expression. Babies may feel “floppy” and can have problems swallowing or breathing.

No known outbreaks of infant botulism tied to powdered formula have previously been confirmed, said Dr. Steven Abrams, a University of Texas nutrition expert.

“This would be extremely rare,” he said.

Infant botulism treatment

The only treatment is known as BabyBIG, an IV medication made from the pooled blood plasma of adults immunized against botulism. California's Infant Botulism Treatment and Prevention Program developed the product and is the sole source worldwide.

BabyBIG works to shorten hospital stays and decrease the severity of illness in babies with botulism. Because the infection can affect the ability to breathe, infants often need to be placed on ventilators.

All of the children in the ByHeart outbreak have received the medication, the CDC said. The treatment is delivered in vials that cost $69,300 apiece, Pan said.

Potential impact on U.S. formula supplies

There is little danger of infant formula shortages because of this outbreak. ByHeart, which was founded in 2016, accounts for an estimated 1% of national formula sales, according to the CDC. The company sells formula through its website and in retail stores nationwide.

That's far different from the crises in late 2021 and 2022, when four infants were sickened by a different germ after consuming formula made by Abbott Nutrition. Two of the babies died. No direct link was found between the Abbott products and the infections caused by cronobacter sakazakii, but FDA officials closed the company's Michigan plant after contamination and other problems were detected.

Abbott recalled top brands of infant formula, triggering a massive nationwide shortage that lasted months.

In 2022, ByHeart recalled five batches of infant formula after a sample at the company's packaging plant tested positive for cronobacter sakazakii, the germ at the heart of the Abbott crisis. In 2023, the FDA sent a warning letter to the company detailing “areas that still require corrective actions.”

Reviewing infant formula ingredients

Federal health officials have vowed to overhaul the U.S. food supply and are taking a new look at infant formula.

Health Secretary Robert F. Kennedy Jr. has directed the FDA to review the nutrients and other ingredients in infant formula, which fills the bottles of millions of American babies.

The effort, dubbed “Operation Stork Speed,” is the first deep look at the ingredients since 1998.

FDA officials are reviewing comments from industry, health experts and public to decide next steps.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.