Pneumonia is a serious lung infection where the tiny air sacs in your lungs, called alveoli, get filled with pus and fluid instead of air. This makes it hard and painful to breathe and limits how much oxygen you can get.
Pneumonia is a serious lung infection where the tiny air sacs in your lungs, called alveoli, get filled with pus and fluid instead of air. This makes it hard and painful to breathe and limits how much oxygen you can get.