How can I differentiate between viral and bacterial pneumonia in a primary care setting?

In primary care, differentiating viral from bacterial pneumonia relies primarily on clinical assessment supported by selective investigations. Key clinical features favouring bacterial pneumonia include a sudden onset of high fever, productive cough with purulent sputum, pleuritic chest pain, and signs of consolidation on chest examination such as bronchial breath sounds and dullness to percussion NICE CG191. Conversely, viral pneumonia often presents with a more gradual onset, lower-grade fever, dry cough, and diffuse wheezing or crackles rather than focal signs NICE CG191.

Point-of-care tests (POCT), such as C-reactive protein (CRP), can aid differentiation. Elevated CRP levels (>100 mg/L) are more suggestive of bacterial infection, whereas lower or moderately raised CRP levels may indicate viral aetiology or atypical pathogens NICE CG191[Benninger & Segreti 2008]. However, CRP should be interpreted alongside clinical findings to avoid overuse of antibiotics NICE CG191.

Pulse oximetry and chest X-ray (if accessible) provide additional diagnostic clues. Hypoxia and lobar consolidation on imaging support bacterial pneumonia, while viral pneumonia may show bilateral interstitial infiltrates NICE CG191.

Recent literature highlights the potential of rapid molecular POCT for respiratory pathogens in primary care. These tests can identify viral agents quickly, helping to reduce unnecessary antibiotic prescribing, but their availability and cost-effectiveness remain variable Nairz & Weiss 2025.

In summary, a combination of clinical features, selective use of CRP testing, and, where possible, imaging and molecular diagnostics, enables differentiation between viral and bacterial pneumonia in primary care. Clinical judgement remains paramount, with guidelines emphasising cautious antibiotic use guided by these assessments NICE CG191[Benninger & Segreti 2008; Nairz & Weiss 2025].