Rising Mycoplasma pneumoniae Cases in Young Children: Q&A With CDC's Dr Adam L. Cohen

Medscape Medical News spoke with the CDC's Adam L. Cohen, MD, MPH, about what healthcare providers need to know regarding the increased number and severity of cases in young patients in the United States. 

On October 18, 2024, the Centers for Disease Control and Prevention (CDC) shared that cases of the bacterial infection Mycoplasma pneumoniae had been increasing since spring of this year, peaked in August, and have remained high since. Notably, cases are being seen in children as young as 2, while the infection has typically been most common among school-aged children, teens, and young adults.

Medscape Medical News spoke with Adam L. Cohen, MD, MPH, a pediatrician and chief of the CDC's Pneumonia and Streptococcus Epidemiology Branch, about what healthcare providers should know, whom to test, and how to treat M pneumoniae.

Text has been edited for length. 

Can you tell us more about M pneumoniae?

With M pneumoniae there are two things to focus on. One is that M pneumoniae is a common cause of pneumonia in respiratory illness in all age groups. It typically presents with respiratory illness symptoms like a cough, a fever, and is known as "walking pneumonia" because, often, it does not cause severe disease and people are able to get up and do things; they just may feel tired and not 100%.

The other piece — and why we are more concerned about it right now — is that we didn’t really detect it in the United States for several years, during the pandemic. Over the past few months, it really has started to circulate and be a more common cause of disease. 

Importantly, we are seeing it now in younger kids, even as young as age 2. It can cause disease in all age groups but, historically, is most common in school-aged children. It has been less commonly identified in that younger pediatric age group.

Over the summer it was one of the leading causes of hospitalizations for pneumonia in younger children.

Why are we seeing such a large increase, especially in children?

We don’t really know why that’s happening. We know that M pneumoniae typically comes in waves. Right before the pandemic, it looked like M pneumoniae cases were starting to rise in the US and then with all the measures to reduce respiratory illness transmission, M pneumoniae in the US was barely identified. Now that we are in a stage where other respiratory illnesses are circulating again, we started to see M pneumoniae again, particularly around the world in Asia and Europe last winter. They started to have a number of M pneumoniae cases and they were seeing it in younger age groups.

This spring, we started to see it come back in the US, but it was at low levels until this summer when it started to peak, and that’s what we’ve been monitoring. We’ve seen something similar to what other places around the world have seen with cases in younger patients, but we don’t really know why that is the case. We are actively looking at the data to see if we can understand what might be causing [increased cases in young patients].

What are the symptoms of M pneumoniae infection?

The most common symptoms are respiratory illness like cough or difficulty breathing, fever, and fatigue, though typically as a mild illness. But it can present with additional symptoms. Though uncommon, it can cause rash, it can affect the brain, and it can cause abdominal symptoms like diarrhea, so those are all things that we look at. 

In younger children, it can present with respiratory and GI symptoms like vomiting or diarrhea. It can cause mucositis, which is somewhat specific for M pneumoniae, but these symptoms are not typically present without other respiratory symptoms.

How contagious is it?

M pneumoniae is transmitted person to person through coughing and sneezing, which means that the best way to prevent transmission is covering your cough, covering your sneeze, and washing your hands.

Generally, if you’re just around someone in a casual way, you may not catch it; it is more spending extended time [around an infected person] that would lead to transmission. And we also see transmission in settings where people are living close together, so that might be in a college dormitory or in a nursing home, where people would have prolonged contact.

With recent data on the uptick in cases in young children, daycare centers may be an area of potential transmission.

For how long can someone with M pneumoniae infection be infectious?

Theres not a lot of data on this; M pneumoniae hasn’t been studied as much as other respiratory pathogens. We know that M pneumoniae can have a long incubation period — 1 to 4 weeks — and people become somewhat contagious even during that period. You also can have prolonged cough and symptoms for a few weeks, so it can be transmitted for a particularly long time just because it is a respiratory illness that can take a while to show up and take a while to resolve.

Which patients are most at risk for complications from M pneumoniae infection?

We particularly have concerns for patients who have underlying respiratory diseases like asthma, who might get hit harder with M pneumoniae. Another group that might be more at risk for respiratory illness complications is pregnant women.

Which patients should be tested for M pneumoniae infection, and how?

We’re really seeing this surge right now in kids and in a larger age range than usual. So while it is not uncommon in a typical winter season to see some M pneumoniae in school-aged children or teenagers (5- to 17-year-olds), now we are seeing that more broadly and particularly in children who are hospitalized, so M pneumoniae should be something that clinicians think about in what to test for and how to treat. 

We also recommend that M pneumoniae be considered for patients with more severe presentations of pneumonia.

If a patient is not responding to beta-lactam treatment for pneumonia, certainly M pneumoniae should be something to consider. M pneumoniae does not have a cell wall, which makes it somewhat unusual as bacteria, but that also means that beta-lactams like amoxicillin do not work against it.

M pneumoniae is often diagnosed through multi-pathogen respiratory testing panels. We recommend that clinicians see what’s available for testing in their area, and we do not recommend serologic testing because it doesn’t give as quick results [as panels] and can be harder to interpret.

Which antibiotics are most effective at treating M pneumoniae infection?

First-line treatment for M pneumoniae infection is macrolides. 

There are relatively low levels of resistance to macrolides in the US — we are monitoring that — but if a patient is diagnosed with M pneumoniae and is not responding to macrolide treatment, then tetracyclines and fluroquinolones are the recommended second-line treatment.

What is CDC doing to address the increase in cases?

We are using all the surveillance systems that we can to monitor this disease, to understand when it’s going up and in what group it’s going up, and also looking at the antimicrobial resistance to see if that would change the recommendations for antibiotic use. And we are analyzing how people are presenting with the disease. While we are seeing right now that it is presenting as a typical respiratory infection, we want to make sure that there isn’t something unusual going on with the bacteria itself or the way it’s showing up that might give guidance in how to treat and prevent it.

Where can clinicians find more information and resources about M pneumoniae infection?

We are interested in hearing about unusual clusters or unusual presentations because that may give us insight about what’s going on. Clinicians can reach out to us to share cases or if assistance is needed in treatment. Contact us at Pneumonia-Strep@cdc.gov

A recent bulletin provides further information on M pneumoniae and real-time recommendations.