Death from pneumonia occurs primarily due to the lungs' impairment in oxygen exchange caused by infection and inflammation filling the alveoli—the tiny air sacs in the lungs—with pus and fluid. This prevents sufficient oxygen from entering the bloodstream and carbon dioxide from being expelled, leading to severe breathing difficulties and reduced oxygen supply to vital organs. In severe cases or in vulnerable individuals (such as the elderly, very young children, or those with weakened immune systems or underlying health conditions), this can cause respiratory failure. Additionally, pneumonia can trigger widespread infection in the body (sepsis), causing blood pressure to drop, organ failure, and ultimately death if untreated. Complications like acute respiratory distress syndrome, lung abscesses, or empyema can also worsen the disease outcome. Prompt treatment with antibiotics, supportive care including oxygen therapy, and addressing complications are critical to preventing death from pneumonia.