A bacterium called Mycoplasma pneumoniae causes two types of respiratory tract infections: the more common chest cold, tracheobronchitis, and the less common lung infection, walking pneumonia. Though we’re in the thick of respiratory illness season, the bacterium can spread year round. This year infections spiked in late spring and have remained high, the Centers for Disease Control and Prevention (CDC) said in mid-October, with the proportion of emergency department patients discharged with a diagnosis of M. pneumoniae-associated pneumonia or acute bronchitis peaking in August.

Such infections tend to be most common among older children and adolescents but in 2024 have been rampant among young children. The CDC reported the following increases in walking pneumonia emergency department visits, as a proportion of pneumonia-associated visits, from March 30 through the week ended Nov. 2:

• 2–4-year-olds: 1.4% to 7%
• 5–17-year-olds: 2.8% to 7.6%
• All ages: 0.5% to 2.8%

Bacterial strain variations generally cause M. pneumoniae infections to peak every three to seven years, according to the CDC. The COVID-19 pandemic, however, interrupted this pattern. After years of low incidence, such bacterial infections reemerged worldwide in 2023.

Pneumonia, which can be bacterial, viral, fungal, or parasitic, comes in many forms. Walking pneumonia is considered atypical, according to Dr. Camille Sabella, a pediatric infectious disease specialist at Cleveland Clinic Children’s.

“Walking pneumonia can be different things. It’s usually not your standard bacterial pneumonia,” Sabella said in an Oct. 28 news release about the uptick in cases. “Walking pneumonia is usually caused by something called mycoplasma pneumonia, but it can also be very similar to viral pneumonias as well.”

How does walking pneumonia spread?

M. pneumoniae spreads via respiratory droplets, so covering your mouth and nose when you cough or sneeze goes a long way in preventing others from getting sick. And because there’s no walking pneumonia vaccine, practicing good hygiene including handwashing is the best way to avoid illness, the CDC says.

Walking pneumonia outbreaks typically occur in these crowded locations:

• College residence halls
• Detention or correctional facilities
• Hospitals
• Long-term care settings
• Military training facilities
• Schools

Despite disease prevalence among children, anyone can catch walking pneumonia—especially people who have a weakened immune system or a preexisting lung condition such as asthma, or are already recovering from a respiratory illness.

Sabella recommends young children get the pneumococcal pneumonia vaccine, which protects against a bacterium called Streptococcus pneumoniae, even though it doesn’t prevent walking pneumonia.

“Every child should be vaccinated against this,” Sabella said. “We start vaccinating against that early in life, and that works very well. But because the pneumococcal bacteria has so many different strains, we can’t protect against every strain with the vaccine that’s currently available.”

What are symptoms of walking pneumonia?

M. pneumoniae can damage the lining of your lungs, throat, and windpipe. Once you’ve been exposed, symptoms may appear within one to four weeks and last several weeks. Or, you may be asymptomatic. If you do show symptoms, the CDC notes they may vary based on whether the bacterium gives you a chest cold or pneumonia:

• Chest cold
  • Children younger than 5
    • Diarrhea
    • Sneezing
    • Sore throat
    • Stuffy or runny nose
    • Vomiting
    • Watery eyes
    • Wheezing
  • People 5 and older
    • Feeling tired
    • Fever
    • Headache
    • Slowly worsening cough
    • Sore throat
• Pneumonia
  • Cough
  • Feeling tired
  • Fever and chills
  • Shortness of breath

No matter the type of M. pneumoniae infection, seek emergency medical care if you or a child in your care have difficulty breathing, or persistent or worsening symptoms.

How do you treat walking pneumonia?

Most health care providers don’t test for M. pneumoniae infection, according to the CDC, but may do so via blood specimen or, more commonly, a nose or throat swab. Depending on your symptoms, they may also order a chest X-ray.

Over-the-counter cough and cold medicine may help ease your symptoms but don’t treat the infection. Your doctor may prescribe a special type of antibiotic medication called a macrolide, as some common antibiotics such as penicillin won’t treat walking pneumonia.

For more on respiratory illnesses:

• Public health experts are warning of a ‘quad-demic’ this winter. Here’s where flu, COVID, RSV, and norovirus are spreading
• Pneumonia can be a deadly complication of COVID, the flu, and RSV: What to know about pneumococcal vaccination
• RSV can be deadly, especially for older adults. What to know about symptoms and the new vaccine
• New flu shots have arrived. Here’s the best time to get your annual vaccine
• Free, at-home COVID tests are back. Here’s how to order yours