Overview

Pneumonia is an infectious condition of the lungs and broader respiratory system. It primarily affects the tiny air sacs called alveoli, which normally transfer oxygen from the air into the bloodstream. When alveoli become swollen with fluid and cellular debris, gas exchange is reduced and breathing becomes difficult. This process involves local inflammation and often accumulation of thick fluid or pus, which together cause the typical signs of the illness.

Causes and risk factors

Pneumonia can be caused by bacteria, viruses, and less commonly fungi or other organisms. It may follow a chest infection or influenza, or arise after inhalation of irritants. People at greater risk include the very young, older adults, those with weakened immune systems, chronic lung or heart disease, and smokers. Hospital-acquired or ventilator-associated pneumonia are distinct clinical situations with different likely organisms.

Symptoms and complications

Common symptoms include cough, fever, rapid or difficult breathing, chest pain when breathing, and general weakness. In severe cases oxygen levels fall and complications such as pleural effusion (fluid around the lung), lung abscess, or bloodstream infection can occur. The severity ranges from mild, outpatient illness to life-threatening disease requiring intensive care.

Diagnosis and treatment

Diagnosis typically combines clinical assessment with chest imaging and laboratory tests of blood and sputum. Treatment depends on the cause: antibiotics for bacterial pneumonia, supportive care and sometimes antivirals for viral causes, and antifungals when relevant. Oxygen therapy, fluids, and respiratory support may be needed for more serious cases.

Prevention and public health

  • Vaccination against common causes such as pneumococcal bacteria and influenza reduces risk.
  • Hand hygiene, avoiding tobacco smoke, and early care for respiratory infections help lower incidence.
  • Public health measures and access to timely medical care have greatly reduced severe outcomes compared with the pre-antibiotic era.

Understanding pneumonia involves recognizing how inflammation of the alveoli impairs oxygen uptake and how prompt diagnosis and appropriate treatment improve recovery. For more information, consult clinical guidelines or trusted health resources: overview, respiratory system reference, alveoli structure, oxygen exchange, air and breathing, inflammation mechanisms, infective fluids.