Just in time for the holidays, a rise in cases of a contagious lung infection across the country is causing alarm, especially for parents of young children.

Ali Rogan talks with an infectious disease specialist about what's behind the spike.

The colder months usually mean more time indoors and higher rates of respiratory illnesses like the flu and COVID.

But now the CDC is tracking an uptick in cases of so-called walking pneumonia.

The respiratory illness usually sickens school-aged children and teens, but this year toddlers are being hit the hardest.

Dr. Donald Dumford is the infectious disease specialist at Cleveland Clinic.

Dr. Dumford, thank you so much for being here.

What is walking pneumonia, and how does it differ from other types of pneumonia?

When we talk about walking pneumonia versus a more classic case of pneumonia,

essentially that it's typically causing a more mild course of illness. If you think about a typical case of pneumonia, essentially that it's typically causing a more mild course of illness.

If you think about a typical case of pneumonia, you're going to see abrupt onset of symptoms,

whereas with walking pneumonia, which is typically caused by a bacteria called mycoplasma,

you're going to see kind of a gradual onset over a few days leading to the illness. So it's

going to be a few days where you start to

feel poorly, you start to get a cough, you start to get a fever. And really over about three to five

days, you get a fever, headache, muscle aches, and then start to get a pretty bad cough with it.

What do we know at this point about why toddlers and other young children are being affected so much this year as compared to previous years?

When you think about mycoplasma, typically we see that about every three to five years, there's a cyclical increase in cases.

So normally, no matter what happens, every three to five years you see a rise.

We really didn't see that rise that we expected during the COVID pandemic.

So I think right now, because we have probably a higher number of susceptible people,

you tend to see that there's a lot of higher cases of severe illness, which is why we're seeing it a lot in the toddler population,

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