Pneumonia (viral)

Viral pneumonias Respiratory viruses are reported in about 10% to 30% of immunocompetent adults hospitalised with CAP. (1) Influenza virus A/B, respiratory syncytial virus, adenovirus, rhinovirus, and parainfluenza virus are the most common viral causes of CAP in immunocompetent adults. (2)

In children:

• the respiratory syncytial virus is the most common agent. It may be indistinguishable from acute bacterial bronchitis or bronchiolitis and is often accompanied by a skin rash. It is unresponsive to antibiotics.
• adenovirus may produce viral pneumonia in children and young adults. It more commonly causes upper respiratory tract disease with prominent rhinitis but on occasion, may produce lower respiratory tract disease, including bronchiolitis and pneumonia.

In adults:

• the principle viral cause of pneumonia is influenza A virus. This usually occurs during epidemics of influenza A - Asian 'flu - but is very rare. The condition develops rapidly with progressive dyspnoea; acute haemorrhagic disease of the lungs may cause death within hours. However, the most common cause of pneumonia during influenza epidemics is secondary bacterial infection, usually with Staphylococcus aureus or Streptococcus pneumoniae.

Other viruses which may affect the lung directly include those of measles, chickenpox and herpes zoster.

Diagnosis is confirmed by a rise in specific antibody titre.

1. Cillóniz C, Ewig S, Polverino E, et al. Microbial aetiology of community-acquired pneumonia and its relation to severity. Thorax. 2011 Apr;66(4):340-6.

2. Jennings LC, Anderson TP, Beynon KA, et al. Incidence and characteristics of viral community-acquired pneumonia in adults. Thorax. 2008 Jan;63(1):42-8.