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. Pneumonia can range in seriousness from mild to life-threatening and is most serious for infants and young children, people older than age 65, and people with health problems or weakened immune systems. Caused by bacteria such as Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, and others. Typically affects one lobe of a lung (lobar pneumonia) or multiple areas throughout both lungs (bronchopneumonia).
