H1N1 influenza

H1N1 influenza is a strain of influenza that notably resulted in a pandemic in 2009.

Pathology

It is type of influenza A virus of swine origin.

Clinical presenation

There can be a wide spectrum of clinical syndromes with patient's ranging from being asymptomatic to having fulminating viral pneumonia, respiratory failure and death.

Radiographic features

Chest radiograph

It can have a variable presentation and a number of features have been described.

CT chest

Described imaging spectrum is broad which each feature being non specific on its own ^2-3:

• ground-glass attenuation: ~70% region (most common)
• bronchial wall thickening: ~45% (next most common)
• confluent consolidation: ~30%
  • patient thought to have worse clinical progression
  • typically tends to be peripheral consolidation involving the lower lobes
  • can also frequently involve all lobes ⁴
• pleural effusion: ~30%
• atelectatic changes: ~25%
• pneumothorax/pneumomediastinum

See also

• viral pneumonia