Pneumonia
An infection of the lung tissue, usually caused by bacteria or viruses, in which the tiny air sacs fill with fluid and inflammation. It causes cough, fever, breathlessness and chest pain, and ranges from a mild illness treated at home to a severe one needing hospital care.
What it is
Pneumonia is an infection of the lungs in which the small air sacs (alveoli) become inflamed and fill with fluid or pus, which interferes with getting oxygen into the blood. It is most often caused by bacteria (commonly Streptococcus pneumoniae) or viruses (including influenza and COVID-19), and less often by other organisms. Most cases are 'community-acquired' — caught in everyday life — while others develop in hospital or after another illness. Typical symptoms are a cough (often bringing up phlegm that may be green, yellow or blood-tinged), fever and chills, breathlessness, chest pain that is often worse on breathing in, a fast heartbeat and feeling generally unwell; in older people it can present less typically, with confusion or simply feeling off. It is diagnosed clinically and usually confirmed with a chest X-ray, supported by blood tests. Severity ranges widely: many people recover at home with antibiotics (for a bacterial cause) and rest, but pneumonia can be serious — especially in the very young, older adults, and those with other health problems or a weakened immune system — and severe cases, or those causing low oxygen or sepsis, need hospital treatment. Vaccination (against pneumococcus and influenza) helps prevent it.
Key lab markers
- Chest X-ray — the usual confirming test; blood tests support severity and cause.
- CRP — typically raised, and higher in bacterial infection; also used to follow the response.
- White cell count and neutrophils — usually raised in bacterial pneumonia.
- Procalcitonin — helps distinguish bacterial from viral infection and guide antibiotics.
- Oxygen level, urea and kidney function — help assess severity (part of severity scores).
- Blood and sputum cultures — identify the organism in more severe cases.
Symptoms
- Cough, often bringing up phlegm (green, yellow or blood-tinged)
- Fever, chills and sweating
- Breathlessness
- Chest pain, often worse on breathing in
- Fast heartbeat and feeling generally unwell
- In older people — confusion or simply feeling off, sometimes without a high fever
Related symptoms
Related lab panels
When to discuss with a doctor
Pneumonia needs medical assessment: see a doctor for a cough with fever and breathlessness, chest pain on breathing, or coughing up discoloured or bloody phlegm, especially if you feel unwell. Seek urgent care for severe breathlessness, blue lips, confusion, a very fast heartbeat, or a high fever with feeling very unwell — these can signal a severe infection, low oxygen or sepsis, particularly in older adults, young children, or people with heart, lung or immune problems. Prompt treatment matters, and many bacterial cases respond well to antibiotics. Vaccination against pneumococcus and influenza reduces the risk. Mediora.AI can highlight a raised CRP, white-cell or procalcitonin pattern that fits an infection and help follow the response to treatment, but pneumonia is diagnosed and treated by a doctor, usually with a chest X-ray.