‘Walking pneumonia’ is surging ahead of cold and flu season

Levels of this milder lung infection—which can lead to “walking pneumonia"—are 10 times greater than last year, according to the Centers for Disease Control and Prevention. Though the CDC doesn’t officially track the disease, it issued an alert last month noting the rise in cases. Levels of walking pneumonia, so named because patients often feel well enough to go about their normal daily activities, typically peak every three to seven years.

Chris Edens, lead of the CDC team that tracks Legionella and atypical pathogens, said the agency saw a rise of cases in late spring. It peaked in August then declined a bit. The decrease might not last, he adds, noting “levels seem to be flattening out or maybe even ticking back up."

Cases of walking pneumonia are up across all age groups, with children 17 and under experiencing the largest rise, says Edens.

Symptoms of the respiratory illness caused by mycoplasma pneumoniae can include cough, fever and a sore throat, say doctors. If the bacteria damages the throat and lungs, the result can be a less severe form of pneumonia.

Someone with typical pneumonia feels ill enough to stay home in bed, but if you have walking pneumonia, it might take an X-ray of your lungs to reveal significant infection, says Edens.

A milder pneumonia

The CDC estimates about two million people a year get mycoplasma pneumoniae infections. Doctors say the real numbers are likely higher, as the infections aren’t closely tracked.

The overwhelming majority of infections are very mild or even asymptomatic, says Edens, and only a small slice evolve into walking pneumonia. The main telltale is a persistent cough: “The symptoms can linger even if they don’t get worse," he says. “It can take a little longer to clear than some other respiratory illnesses."

Dr. Casey Burg, division chief of pulmonary, allergy and sleep at Children’s Nebraska in Omaha, has seen a large number of walking pneumonia cases in outpatient clinics and some in the hospital. Burg estimates it takes about two weeks to go away, “a little bit longer than you would think if you have a cold."

In very rare instances it can evolve into severe pneumonia, worsening asthma or encephalitis, requiring hospitalization.

Pneumonia is inflammation in the lungs caused by a variety of viruses and bacteria. Typically, it’s treated with amoxicillin or other related antibiotics. But walking pneumonia responds to other drugs, such as azithromycin, commonly known as a Z-Pak, says Dr. Graham Snyder, medical director of infection prevention and hospital epidemiology at the University of Pittsburgh Medical Center.

Snyder says listening to a patient’s lungs can help diagnose pneumonia but you don’t know what bacteria is causing it without a lab test with a back-of-the-nose swab.

For many patients, the infection resolves before they ever need to see a doctor.

What you can do

Snyder said his region is seeing more adults and children testing positive for walking pneumonia, similar to national trends. Most of the illness is spread through droplets from coughing and sneezing, he says. He recommends frequent handwashing, masking if you’re sick and staying home if you’re feeling unwell.

Children or adults who are immunocompromised or have underlying conditions such as asthma or chronic obstructive pulmonary disease are more at risk for developing serious illness.

Burg recommends seeing a doctor if you have difficulty breathing or symptoms are beyond what you expect with a mild to moderate cold. Also, see a doctor if you or your children are having symptoms and there are outbreaks in your neighborhood or school system. Early treatment can shorten the duration of the illness and help prevent its spread.

Mycoplasma pneumoniae isn’t as infectious as Covid-19 or measles, which spread more easily through the air. And the incubation period—the time between your first exposure and when your symptoms show up—can be relatively long, at one to four weeks.

“If you have passing contact, you’re not likely to get it," says Snyder. “It’s really something that transmits effectively when people are in close contact, in households or schools or college dorms."

Write to Sumathi Reddy at Sumathi.Reddy@wsj.com