Pneumonia is an infection of the lungs that inflames the air sacs, causing cough, fever, and breathing difficulty; it can be life-threatening in infants, older adults, and people with chronic illness.

Infectious Diseases

Pneumonia

2025-09-15

Intro

Pneumonia is a lung infection that inflames the air sacs (alveoli). Fluid and pus can fill the sacs, making oxygen exchange harder. While many cases are mild, pneumonia can be severe or fatal in vulnerable people, so early diagnosis and treatment matter.

Key Points

Caused by bacteria, viruses, or fungi; severity ranges from mild to life-threatening.
Symptoms: cough, fever, breathlessness, chest pain, fatigue.
High-risk: young children, older adults, smokers, chronic disease, immunosuppression.
Treatment depends on cause: antibiotics (bacterial), supportive care, sometimes antivirals or antifungals.
Prevention: vaccination, hand hygiene, smoking cessation, prompt treatment of respiratory infections.

Background

Community-acquired pneumonia (CAP) develops outside hospitals; hospital-acquired and ventilator-associated cases occur during/after healthcare exposure and are often more severe or drug-resistant.

Causes or Mechanisms

Pathogens reach alveoli via inhalation or aspiration. The immune response leads to inflammation and consolidation, impairing gas exchange and causing systemic symptoms.

Diagnosis / Treatment / Options

Diagnosis: history/exam, pulse oximetry, chest X-ray, +/- labs (CBC, CRP), and in moderate-severe cases, cultures/viral tests.
Treatment:

Outpatient, mild: oral antibiotics if bacterial is likely; rest, fluids, antipyretics.
Severe or high-risk: hospitalization, IV antibiotics, oxygen; manage complications (e.g., effusions).
Viral pneumonia: supportive care ± antivirals (e.g., influenza).
Source control: drain empyema; treat aspiration risk.

Risks / Benefits / Prognosis

Most healthy adults recover fully; risks rise with age/comorbidities. Complications include respiratory failure, sepsis, empyema, and prolonged fatigue.

FAQ

Q: How long until I feel better?
A: Fevers settle in 3–5 days; cough/fatigue can persist for weeks. Seek review if not improving.