Overview
Pneumonia is an infection that inflames the air sacs in one or both lungs, which may fill with fluid or pus, causing cough with phlegm, fever, chills, and difficulty breathing. It can be caused by bacteria, viruses, or fungi. Pneumonia can affect anyone but is particularly serious for infants, elderly people, and those with weakened immune systems or chronic health conditions. Most healthy adults recover completely.
Causes and risk factors
The following factors are associated with the development of Pneumonia:
- Bacterial pneumonia: Streptococcus pneumoniae most common
- Viral pneumonia: influenza, COVID-19, respiratory syncytial virus
- Fungal pneumonia: in immunocompromised individuals
- Aspiration pneumonia: inhaling food, drink, or vomit
- Hospital-acquired pneumonia
- Weakened immune system
- Chronic lung or heart disease
- Smoking
- Older age
- Recent respiratory illness
Signs and symptoms
Common signs and symptoms of Pneumonia include:
- Cough producing yellow, green, or blood-tinged phlegm
- Fever, sweating, and shaking chills
- Shortness of breath
- Sharp chest pain when breathing or coughing
- Fatigue and weakness
- Nausea, vomiting, or diarrhoea
- Confusion in older adults
- Low oxygen levels (cyanosis)
- Rapid breathing and heart rate
Diagnosis
Pneumonia is typically diagnosed through a combination of medical history, physical examination, and appropriate investigations such as blood tests, imaging, or specialist review, depending on the specific condition and presentation. Your doctor will consider all relevant symptoms and risk factors before making a diagnosis.
Treatment options
Treatment approaches for Pneumonia may include:
- Antibiotics for bacterial pneumonia (amoxicillin, doxycycline)
- Antiviral medications for viral pneumonia
- Antifungal medications for fungal pneumonia
- Hospitalisation for severe cases
- Oxygen therapy if blood oxygen low
- IV fluids and fever management
- Rest and adequate hydration
- Vaccinations to prevent pneumococcal pneumonia and flu
Prevention
Pneumococcal vaccine, flu vaccine annually, COVID-19 vaccine, stop smoking, practice good hand hygiene, stay healthy.
Complications
If left untreated or poorly managed, Pneumonia can lead to complications including:
Bacteraemia (blood infection), lung abscess, pleural effusion, respiratory failure, sepsis, and death.
Sources and references: This article is written in accordance with NHS UK, WHO, and Mayo Clinic clinical guidelines. It is reviewed for accuracy by the SymptomSense content team. ICD-10 code: J18. Last reviewed June 2026.