Bacterial infections from Mycoplasma pneumoniae, which can cause walking pneumonia, have surged since late spring, according to the CDC. The spike has been highest in children ages 2-4. Cases of "walking pneumonia" — a milder form of the lung infection pneumonia — have spiked in the United States, particularly among young children.

Walking pneumonia cases are surging among young children in the United States, federal health officials warn.

According to the CDC, respiratory infections caused by the bacteria Mycoplasma pneumoniae have increased in the U.S. over the past six months, particularly among young children. In previous years, most pneumonia or acute bronchitis infections caused by the bacteria were found in school-aged children and teens.

Dr. Johnna Wilson, a pediatric critical care doctor with Deaconess Hospital, said mycoplasma pneumonia cases increase every three to five years.

Infections with the illness known as walking pneumonia have been surging across the United States at unusually high levels in young kids, according to emergency room data from many states. Doctors say most of those affected by the infection,