Walking pneumonia cases are surging among young children in the United States, federal health officials warn.
"Bacterial infections caused by Mycoplasma pneumoniae increased in the United States since late spring and have remained high," a statement issued Friday by the U.S. Centers for Disease Control and Prevention noted. "The proportion of patients discharged from emergency departments with a diagnosis of M. pneumoniae-associated pneumonia or acute bronchitis has been increasing over the past six months, peaking in late August."
The worst rates of the illness have been seen in young children ages 2 to 4, according to the agency.
"The increase in children ages 2–4 years is notable because M. pneumoniae historically hasn't been recognized as a leading cause of pneumonia in this age group," the CDC added.
Close to 7% of emergency room visits with pneumonia in this age group were diagnosed with the bacteria through late September. This has "dropped slightly" from a peak of more than 10% in August, the CDC said.
An agency spokesperson told CBS News that levels are the worst right now in the middle of the country, from Texas through Iowa.
But other states are starting to report surges in walking pneumonia cases.
Wisconsin's health department said Friday that it had received reports of increasing "unusual pneumonia cases" in kids and young adults from doctors around the state.
"The Wisconsin Department of Health Services [DHS] has received multiple notices from clinicians statewide regarding an increased incidence of unusual pneumonia cases among school-aged children and young adults," state health officials said. "These cases are suspected to be infections caused by the bacteria M. pneumoniae."
Meanwhile, health officials in Illinois announced Thursday that they had tracked "several clusters reported in schools throughout the state," alongside increases seen in data from testing labs.
"M. pneumoniae is exclusively a human pathogen, which primarily causes respiratory infections. Infections can occur in the upper and lower respiratory tract. Common manifestations include pharyngitis, pneumonia, and tracheobronchitis," Illinois health officials said. "The bacteria can also cause a wide array of extra-pulmonary manifestations often without obvious respiratory disease. These include neurologic, cardiac, hematologic, rheumatologic and skin complications. Notably, approximately 10% of children with M. pneumoniae infection exhibit a rash..."
The number of rhinovirus and enterovirus cases reported to the CDC have also surged in recent weeks, nearing peaks seen during previous fall waves of the diseases.
"It's likely to worsen with pollen and mold counts rising, colder weather keeping everyone inside and the holidays bringing people together," Virginia-based health system VCU Health said last week. In the central part of that state, pediatric pneumonia cases requiring hospitalization are up 30%.
Dr. Marian Michaels, a professor of pediatrics and surgery at Children's Hospital of Pittsburgh, told CBS News that it was "too early to tell for sure" if this year's wave would amount to an unusual increase in hospitalized patients.
Michaels was the co-author of a report published earlier this year by the CDC which found kids sickened with the bacteria increased last year but remained lower than before the pandemic.
"The numbers are perhaps increasing a bit, but are still below the pre-pandemic levels for now," Michaels noted.