Pneumonia is inflammation and infection of the lungs. It usually affects the small air sacs where oxygen passes into the blood, causing them to fill with fluid or pus. Pneumonia can be mild, but it can also become serious, especially in older adults, babies, young children and people with heart, lung or immune-system problems.
Most cases are caused by bacteria or viruses. Less commonly, fungi, aspiration of stomach contents, or hospital-related infection can be involved.
Symptoms
Common symptoms include a cough, fever, sweating or shivering, shortness of breath, chest pain that is worse when breathing or coughing, tiredness, loss of appetite and feeling generally unwell. The cough may produce yellow, green, brown or blood-stained phlegm.
Older people may present with confusion or a sudden decline rather than obvious chest symptoms. Babies and young children may have fast breathing, poor feeding, drowsiness or grunting.
Causes and Types
Community-acquired pneumonia starts outside hospital. Hospital-acquired pneumonia develops during or shortly after a hospital stay and can involve different organisms or more resistant bacteria. Aspiration pneumonia happens when material such as food, liquid or vomit enters the lungs.
The most common bacterial cause is often Streptococcus pneumoniae, but the exact cause is not always identified. Viral pneumonia can follow infections such as influenza, COVID-19 or respiratory syncytial virus.
Diagnosis
Diagnosis is based on symptoms, examination and, when needed, tests such as oxygen saturation, blood tests, sputum tests and a chest X-ray. A clinician may listen for crackles or reduced breath sounds.
Severity is important. Someone with low oxygen levels, confusion, low blood pressure, dehydration, severe breathlessness, chest pain, or a high-risk background may need urgent assessment or hospital care.
Treatment
Treatment depends on the likely cause and severity. Bacterial pneumonia is usually treated with antibiotics. Rest, fluids and pain or fever relief may also help. People with mild pneumonia often recover at home, while severe cases may need hospital treatment with oxygen, intravenous antibiotics, fluids or breathing support.
Most people start to improve after treatment, but recovery time varies. Asthma + Lung UK notes that many people feel better within 2 to 4 weeks, although tiredness and breathlessness can last longer.
Prevention
Prevention includes vaccination where eligible, stopping smoking, hand hygiene, reducing exposure to respiratory infection, and managing long-term conditions such as asthma, COPD, diabetes or heart disease.
Vaccines that may reduce pneumonia risk include pneumococcal vaccination, annual flu vaccination and COVID-19 vaccination for eligible groups.
Complications
Possible complications include pleural effusion, lung abscess, sepsis, respiratory failure and worsening of existing heart or lung disease. Prompt treatment is especially important for people who are frail, immunosuppressed or already unwell.
See Also
References
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