December 3, 2009

H1N1 (Swine Flu) Pneumonia

Chest radiograph shows patchy airspace opacities in bilateral mid to lower lung zones in a patient infected with H1N1 virus (lab confirmed), admitted to the ICU. Subsequent CT (not shown) reveals similar findings without pleural effusions or lymphadenopathy.

  • First reported in Mexico in April 2009
  • Fatality rate 0.45%
  • Confirmed case = a person with an influenza-like illness with laboratory confirmed novel influenza A (H1N1) virus infection by one or more of the following tests: real-time RT-PCR, viral culture
  • Influenza-like symptoms = fever, cough, sore throat, body aches, headache, chills, fatigue
Radiographic Appearance
  • Initial exam is normal in nearly half of cases who had radiography
  • When initial exam is abnormal, the abnormality is patchy consolidation (50%), groundglass opacity or groundglass opacity with consolidation (25%)
  • Predominant location: lower lung zones (70%), diffuse (25%)
  • Pleural effusion not common (less than 10%)
  • Lymphadenopathy uncommon
Based on a single, uncontrolled study:
  • Patients with abnormal initial radiograph were associated with admission and severe disease
  • H1N1 infection was associated with a high rate of pulmonary embolism (36%) among patients admitted to the ICU

Agarwal PP, Cinti S, Kazerooni EA. Chest radiographic and CT findings in novel swine-origin influenza A (H1N1) virus (S-OIV) infection. AJR 2009;193:1488-1493.

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