With the spike in infections primarily affecting young children, the Fox News senior medical analyst speaks about common sources, symptoms and treatments. Cases of so-called "walking pneumonia" are spiking across the U.S.

, the Centers for Disease Control and Prevention (CDC) has alerted. The highly contagious infection has primarily affected young children , according to the same source. Between March 31 and Oct.

5 of this year, the percentage of cases grew from 1% to 7.2% among children ages 2 to 4, and from 3.6% to 7.

4% among those ages 5 to 17, the agency stated. AMID CHILDHOOD PNEUMONIA OUTBREAKS, INFECTIOUS DISEASES EXPERT REVEALS KEY FACTS ABOUT ‘WHITE LUNG SYNDROME’ Fox News Digital spoke on camera with Dr. Marc Siegel, senior medical analyst for Fox News, about what people should know about this condition.

What is walking pneumonia? Cases of so-called "walking pneumonia" are spiking across the U.S., the Centers for Disease Control and Prevention has alerted.

(iStock) Also known as "atypical pneumonia," walking pneumonia is a "mild lung infection," as defined by Cleveland Clinic. It tends to feel like a bad cold or the flu . Typically caused by bacteria, viruses or mold exposure, the condition causes swelling in the airways and fluid in the lungs.

BIRD FLU LEAVES TEEN IN CRITICAL CONDITION AFTER COUNTRY'S FIRST REPORTED CASE "Walking pneumonia is less than a full lobar pneumonia, where an entire region of the lungs is whited out from a bacteria or virus," Siegel to.