"Our data suggest that severe disease and mortality in the current outbreak is concentrated in relatively healthy adolescents and adults between the ages of 10 and 60 years, a pattern reminiscent of the W-shaped curve [rise and fall in the population mortality rate for the disease, corresponding to age at death] previously seen only during the 1918 H1N1 Spanish pandemic," the authors write.

Patients with 2009 influenza A(H1N1) infection-related critical illness experienced symptoms for a median (midpoint) of four days before entering the hospital, but worsened rapidly and required care in the ICU within one or two days. Shock and multi-system organ failure were common, and 136 patients (81 percent) received mechanical ventilation, with the median duration being 12 days. The average ICU stay was 12 days. Lung rescue therapies included neuromuscular blockade, inhaled nitric oxide and high-frequency oscillatory ventilation.

"In conclusion, we have demonstrated that 2009 influenza A(H1N1) infection-related critical illness predominantly affects young patients with few major comorbidities and is associated with severe hypoxemic respiratory failure, often requiring prolonged mechanical ventilation and rescue therapies," the authors write. "With such therapy, we found that most patients can be supported through their critical illness."

Source: JAMA and Archives Journals