GEOFF BENNETT: An outbreak here in the U.S.

of infant botulism, a rare but serious illness caused by toxins that attack the nervous system, is causing alarm among regulators and parents, prompting an investigation and a nationwide recall of ByHeart Whole Nutrition infant formula.

Stephanie Sy has more.

STEPHANIE SY: According to the Food and Drug Administration, there have been 15 hospitalizations of infants across 12 states.

No deaths have been reported.

Hanna Everett, a mother in Kentucky, experienced this firsthand.

Her four-month-old, Piper, was hospitalized over the weekend.

HANNA EVERETT, Mother: Noticing the recall and I just -- in my gut, I was like, yes, we need to take her.

Her gag reflex was not intact.

It's like -- it becomes paralyzed.

She's going to make a full recovery.

They said we just got very lucky to catch it as early as we did.

STEPHANIE SY: For a closer look, I'm joined by Helena Bottemiller Evich.

She's the founder of Food Fix, a publication that covers food policy in depth.

Helena, thank you for joining the "News Hour."

First of all, how sick are babies who have gotten infant botulism linked to this baby formula they're getting?

HELENA BOTTEMILLER EVICH, Food Fix: Well, 15 hospitalizations is something that is very concerning.

We have not seen botulism tied to infant formula in this country.

We have certainly not seen an outbreak.

These babies are requiring a lot of intervention at the hospital.

The key is to catch it early.

So any signs of poor feeding, difficulty swallowing, loss of head control, if your baby has had this formula and seems off, you should talk to your doctor as soon as possible.

STEPHANIE SY: Last week, California's Department of Health identified botulism in preliminary testing of an opened can of ByHeart formula that had been given to a baby who later was discovered to have botulism.

Earlier, we spoke with Dr.

Erica Pan, the director of California's Department of Public Health.

DR.

ERICA PAN, Director, California Department of Public Health: Infant botulism is what we call a sporadic disease.

It's almost never been seen in an outbreak.

So, right, this is the first time we have seen it linked to a specific formula.

The spores that this bacteria creates can live in dirt and soil.

So, often, most cases of infant botulism, we actually don't find out what the exact source was.

Infant formula should be sterile.

It shouldn't have either dirt or bacteria in it.

So how did this contamination happen?

It's what I'm concerned about, both for this product, but also in the future, so this can be prevented.

STEPHANIE SY: So you heard, Helena, that there is a lot of mystery around how this bacteria could have contaminated formula.

The FDA commissioner said in an interview this week that the supply chain for formula could be stronger.

Do you see ways that this could have been prevented from a policy perspective?

HELENA BOTTEMILLER EVICH: Well, I think the results of the investigation here are going to matter a whole lot, and it absolutely raises key scientific and policy questions.

Right now, we have no requirements to test for botulism because it has not been considered a hazard that we need to be concerned about an infant formula.

But whenever they get to the root cause and figure out what went wrong here, certainly, there's going to be a hard look or there should be a hard look to make sure that this never happens again.

We -- these infants can get quite, quite sick.

This is essentially creating a neurotoxin in their body.

And so this is an extremely serious situation, and absolutely federal health officials are going to need to, A, get to the bottom of this, and, B, figure out what can be done to make sure this never happens again.

STEPHANIE SY: This ByHeart brand of formula makes up only 1 percent, I understand, of the baby formulas on the market nationwide.

You said that parents should be concerned, but is the recall, from what you're seeing, likely to be an isolated case of this one brand, or is it possible that it expands to other brands?

Should parents outside of those that have bought this formula be concerned?

HELENA BOTTEMILLER EVICH: Well, as of right now, it is just this brand.

The really good news here is, this brand only makes up about 1 percent of the formula market.

So there is not a concern about shortages or any major disruptions to the infant formula supply.

I covered the infant formula crisis a few years ago really closely.

It was an incredibly traumatic event for millions of families.

We do not expect that to be the case here.

So that is the good news.

I do think that there are some concerns around just increased cases of infant botulism generally.

So health officials are very confident that ByHeart is connected to what is going on with those 15 infants.

But there are also dozens of other botulism cases that health authorities are now investigating, and they don't know the source.

As California mentioned, these are usually sporadic cases, so you often do not know the source.

As a mom, I have a lot of concerns about whether or not health officials can get to the bottom of all those cases.

We usually only see about 100 botulism infant cases per year.

And FDA said in their most recent update that we have seen about 83 cases just in the last few months.

And so I do hope that health officials have the resources they need to get to the bottom of all these cases and really make sure that there isn't some sort of emerging issue that parents need to know about, that health officials need to be tackling.

STEPHANIE SY: How would you rate the FDA's response to what's happened and their investigation in this recall?

HELENA BOTTEMILLER EVICH: So, right now, we don't know a whole lot about the timeline here.

We know that infants started getting sick in August, and we are now in November.

It often does take time to connect the dots in these cases.

And so I have a lot of questions about how the rest of this investigation is going to unfold.

Right now, it looks like, as soon as we figured out the connection to ByHeart formula, both the company and FDA acted quickly.

But as more comes out about this investigation, I do think there will be a lot of eyes on the FDA once again to make sure that the agency is acting quickly and making sure that families are protected in these situations.

STEPHANIE SY: That is Helena Bottemiller Evich of Food Fix.

Thank you so much.

HELENA BOTTEMILLER EVICH: Thank you.