The Centers for Disease Control and Prevention is sounding the alarm over increased cases of lung infections in the U.S., especially among children, as flu season begins.

According to the CDC, infections caused by mycoplasma pneumoniae have increased over the past six months, leading to an increase in patients discharged from medical centers with pneumonia or bronchitis.

The CDC said it is actively tracking cases of pneumonia and bronchitis in the U.S. and is working to determine the causes of the increase.

“CDC is closely tracking the recent rise in M. pneumoniae infections using various surveillance tools to better understand any differences in demographics, severity of illness, and outcomes as compared to M. pneumoniae infections prior to the COVID-19 pandemic,” the agency said in a statement. “CDC is also reaching out to healthcare providers and health departments to raise awareness of increasing M. pneumoniae infections and working to monitor for antibiotic resistance.”

While infections related to mycoplasma pneumoniae are common, the CDC says there has been a significant increase in childhood cases. From March to Oct. 2024, the proportion of mycoplasma pneumoniae-related infection in children ages 2-4 increased from 1% to more than 7%. Similarly, in the 5 to 17 age range, cases increased from 3.6% to 7.4%.

Overall, the CDC found that the infection rate for diseases caused by mycoplasma pneumoniae has gone up for all age groups from 0.7% in March to 3.3% in Oct.

Mycoplasma pneumoniae bacteria is spread through bodily fluids, typically when someone coughs or sneezes. Outbreaks are common in crowded spaces like restaurants or schools, which could account for the increased cases among children.

Symptoms are mild and manifest slowly and include fever, cough and headache. The infection’s mild symptoms can lead some to believe they have a simple chest cold and decide not to stay home.