It’s officially flu season, so be sure to wash your hands, cover your mouths, and take extra care of yourself this winter. Especially since you may not be able to stroll easily past walking pneumonia.

The U.S. Centers for Disease Control and Prevention has reported a significant surge in walking pneumonia cases this year, specifically among young children. There are a total of about 2 million cases in the U.S. each year.

Over a six-month period, the percentage of cases among children between 2 and 4 years old increased by 6 percentage points, as the share of emergency room cases that resulted in a walking pneumonia diagnosis went from 1% to more than 7%.

Caused by bacteria, walking pneumonia feels quite like the common cold. It commonly spreads through respiratory droplets spread through the air. Symptoms often include a sore throat, sneezing, coughing, headaches, and fever.

Walking pneumonia attacks the lower respiratory system, often resulting in patients developing deep, persistent coughs, chest pains, and shortness of breath several days after infection. The common cold, on the other hand, targets the upper respiratory system.

The most common treatment for walking pneumonia is antibiotics. However, walking pneumonia outbreaks tend to last longer than other respiratory virus outbreaks because it has a longer incubation period and people tend to be contagious longer.

Because there’s no vaccine for walking pneumonia, there isn’t much parents can do once their child becomes sick. Patients are advised to remain at home while they are ill, going to the hospital only if they begin to have trouble breathing or become dehydrated.