When only H1N1 infection was present, the oxygenation deficit was the leading clinical symptom. In cases with prolonged treatment (reinfection or concomitant infection with HSV, Mycoplasma) hypercapnia also was notable. Therefore, one patient received ECMO and one patient ILA therapy (Figure 1 ). The patient with ECMO therapy demonstrated improved oxygenation and normocapnia but deceased due to intracranial bleeding. This patient had histologic confirmed HSV pneumonia for 4 weeks without improvement after acyclovir/foscarnet treatment. A similar clinical pathway was observed in the two other patients who died.