Pneumonia

Pneumonia is an infection that inflames the air sacs in one or both lungs. The air sacs may fill with fluid or pus (purulent material), causing cough with phlegm or pus, fever, chills, and difficulty breathing. Viruses that infect your lungs and airways can cause pneumonia. The flu (influenza virus) and the common cold (rhinovirus) are the most common causes of viral pneumonia in adults. Respiratory syncytial virus (RSV) is the most common cause of viral pneumonia in young children.