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 and reducing oxygen in the blood.

Symptoms

Common symptoms include cough (often producing phlegm), fever, chills, difficulty breathing, chest pain that worsens with breathing or coughing, and fatigue. In older adults, confusion or a lower-than-normal body temperature can be the most prominent sign instead of a high fever.

Causes

Pneumonia can be caused by bacteria, viruses (including flu, RSV, and COVID-19), or, less commonly, fungi. It often develops after another respiratory infection like the flu or a cold weakens the lungs' defenses, allowing a secondary infection to take hold — one reason a cold or flu that suddenly worsens deserves attention.

Who Is at Higher Risk

Young children, adults over 65, smokers, and people with chronic conditions (such as asthma, COPD, heart disease, or diabetes) or weakened immune systems face a significantly higher risk of severe illness, hospitalization, or complications from pneumonia. Pneumococcal and annual influenza vaccination lower the risk of pneumonia and its complications, and are especially recommended for these higher-risk groups.

Treatment

Bacterial pneumonia is treated with antibiotics; viral pneumonia is managed with supportive care, and sometimes antivirals depending on the cause. Many mild-to-moderate cases are treated at home with rest, fluids, and fever/pain control, but this decision should be made by a doctor who has assessed severity, not self-diagnosed.

When It's an Emergency

Seek emergency care for difficulty breathing, bluish lips or face, chest pain, confusion, or a persistently high fever — these can indicate a severe case needing hospital-level care, especially in the higher-risk groups above. In infants and young children, watch for different signs of severe illness — fast or labored breathing, grunting with each breath, chest indrawing (the skin pulling in between or under the ribs with each breath), difficulty feeding or drinking, or unusual lethargy — and seek emergency care if any of these appear, even without a high fever.