What is Pneumonia?

Pneumonia is an infection that inflames the air sacs in one or both lungs, which can fill with fluid or pus, making breathing difficult. It's most commonly caused by bacteria or viruses and can range from mild to life-threatening, particularly in young children, older adults, and those with weakened immune systems.

Common symptoms include cough (often producing phlegm), fever, chills, chest pain that worsens with breathing, and shortness of breath. Some people, especially older adults, may have milder or less typical symptoms, such as confusion rather than a high fever.