What is pneumonia

Last updated: April 1, 2026

Quick Answer: Pneumonia is a lung infection that causes inflammation in the air sacs (alveoli), which may fill with fluid or pus, making it difficult to breathe and potentially limiting oxygen absorption.

Key Facts

Understanding Pneumonia

Pneumonia is an infection of the lungs in which the alveoli (tiny air sacs) become inflamed and fill with fluid or pus. This inflammation and fluid accumulation prevents oxygen from being properly absorbed into the bloodstream, leading to symptoms like cough, fever, and difficulty breathing. Pneumonia can range from mild (sometimes called "walking pneumonia") to severe, requiring hospitalization.

Types of Pneumonia

Bacterial pneumonia is the most common type in adults, often caused by Streptococcus pneumoniae. Viral pneumonia is frequently caused by influenza or rhinovirus and often less severe than bacterial pneumonia. Fungal pneumonia typically affects immunocompromised individuals, and aspiration pneumonia results from inhaling food, liquids, or stomach contents. Each type requires different treatment approaches.

Symptoms and Signs

Common symptoms include persistent cough (with or without sputum), high fever, chills, shortness of breath, and chest pain that worsens with breathing or coughing. Some people experience fatigue, loss of appetite, and confusion, particularly elderly patients. Symptoms typically develop 1-3 days after contracting a respiratory infection.

Risk Factors and Causes

Pneumonia risk increases with age over 65, smoking, chronic diseases like diabetes or COPD, weakened immune system, recent surgery, or prolonged bed rest. Children under 5, particularly those in crowded settings, are also at higher risk. Previous respiratory infections and hospitalization are additional risk factors.

Diagnosis and Treatment

Diagnosis involves clinical evaluation, chest X-rays, and sometimes sputum culture or blood tests to identify the causative organism. Bacterial pneumonia requires antibiotics, while viral pneumonia is treated with supportive care including rest, fluids, and fever management. Hospitalization may be necessary for severe cases. Recovery typically takes 1-3 weeks for uncomplicated pneumonia.

Related Questions

What is the difference between pneumonia and bronchitis?

Bronchitis affects the airways (bronchi) causing inflammation and mucus production, while pneumonia affects the air sacs (alveoli) causing inflammation and fluid accumulation. Pneumonia is typically more severe and may cause fever and difficulty breathing.

How is pneumonia diagnosed?

Pneumonia diagnosis involves a physical examination, chest X-ray to visualize lung inflammation, and sometimes sputum culture or blood tests. Doctors may also check oxygen levels and lung function to assess severity.

How long does it take to recover from pneumonia?

Uncomplicated pneumonia typically resolves in 1-3 weeks with appropriate treatment. However, fatigue and cough may persist longer. Recovery time depends on severity, age, overall health, and whether antibiotics were started promptly.

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Sources

  1. Centers for Disease Control and Prevention - Pneumonia Public Domain
  2. Wikipedia - Pneumonia CC-BY-SA-4.0