JOHN YANG: As family and friends gather this holiday season, there's a warning for new parents.

The CDC says cases of whooping cough or pertussis, remain elevated this year.

In Kentucky this week, an unvaccinated infant died from the illness, the third child to die of whooping cough in the state this year.

Other states across the country, including Texas, Florida, California and Oregon, are also experiencing a surge of cases.

Ali Rogin spoke with Dr.

Lorne Walker, a pediatric infectious disease specialist.

ALI ROGIN: Thank you so much for joining us.

First of all, can you just tell us what is whooping cough, what are the characteristic signs of it and what I should people look out for?

DR.

LORNE WALKER, Pediatric Infectious Disease Specialist: So whooping cough is an infection that used to be very common.

It's caused by a bacteria called pertussis.

And the old kind of classic name for it is the hundred day cough.

And it's famous for causing long term respiratory illness.

And in older kids and adults, the primary symptom is very severe, prolonged bouts of coughing and coughing that can be severe enough to cause a collapsed lung or a broken rib.

And so obviously, it's something that makes people pretty sick.

It turns out that the groups that are at the highest risk with whooping cough are people who have compromised immune systems.

So folks who have cancer or who are transplant recipients, but especially young babies.

And one of the challenges with little babies is that instead of having coughing spells, they often will just stop breathing, which is a reason that those kids will often come into the hospital or even need ICU care with a breathing tube to help them breathe.

And so that's why we vaccinate starting at 2 months of age to try and protect that population that's so vulnerable to severe disease with whooping cough.

ALI ROGIN: And so why is it that whooping cough might cause worse symptoms in an infant than it would in a older child or an adult?

LORNE WALKER: We think that in babies, it's a combination of their immature immune system as well as the immature sort of breathing responses that they have to infections like this.

So it's very inflammatory and irritating to the lungs.

And if you're an older kid or an adult, you cough.

But unfortunately, in the little babies, they'll stop breathing, and they'll stop breathing kind of unexpectedly.

ALI ROGIN: There are these three tragic deaths so far that we know of in Kentucky, which are the first deaths that state has seen from this disease since 2018.

What do we know about the frequency of whooping cough diagnoses right now?

Has there been an uptick?

And is what we are seeing now unusual?

LORNE WALKER: 2024 and '25 have both been very difficult years for whooping cough here in the United States.

Here in Oregon in 2025, we've had more than 1,300 cases, which is the highest number since 1950.

And we've had more than 33,000 cases across the country.

And it's not just Oregon where we're seeing a lot of cases, but also in states like Texas and Washington, we've been seeing unusually high numbers of whooping cough cases.

ALI ROGIN: So the CDC says that these whooping cough numbers are higher even than they were before the pandemic.

Why do you think that is?

LORNE WALKER: Unfortunately, the rates of vaccination against whooping cough have been falling for years, even going back prior to the COVID pandemic.

Currently in Oregon, one out of every five 2-year olds hasn't completed their full whooping cough series of vaccinations.

And one out of every 10 kindergartener that's starting school and being exposed to lots of other kids.

And people are not up to date on their whooping cough vaccines.

And we're pretty confident that the low rates of vaccination are the key risk factor for having this high number of cases.

ALI ROGIN: When we talk about children who aren't getting this vaccine, is it possible to figure out how many haven't completed this five-dose course of this particular vaccine and how many are because they're not getting it at all because of something like vaccine hesitancy?

LORNE WALKER: We know that kids are the most protected when they have the full course of precise vaccination.

We start at 2 months of age because we know that the young kids and babies are at the highest risk.

Certainly misinformation and myths about vaccination are one of the drivers of low vaccine rates.

Unfortunately, that's not a new phenomenon.

Misinformation and myths about vaccines started 200 years ago when we had our first smallpox vaccine, which obviously worked because we don't have smallpox anymore.

But that the misconceptions about vaccination I think are a real driver of people being reluctant to vaccinate.

ALI ROGIN: And as families travel for the holidays and they might be worried about encountering a disease like this, especially if they have a young child, what should families be mindful of?

LORNE WALKER: A lot of the things that we all got used to and learned during the COVID pandemic, like washing our hands, covering our coughs, or maybe staying a little bit further away if you're having symptoms of a respiratory infection, all help prevent spread of all infections.

But for these vaccine preventable illnesses like whooping cough, not only having children vaccinated, but having the folks around them vaccinated will help protect everybody.

ALI ROGIN: Dr.

Lorne Walker at Doernbecher Children's Hospital, thank you so much.

LORNE WALKER: Thanks so much for having me.

JOHN YANG: Still to come on PBS News Weekend, why so many Americans who are gainfully employed can't afford a home and the women who saved countless lives at sea as lighthouse keepers.