Pneumonia and the acute respiratory distress syndrome (ARDS) account for the majority of severe morbidity and mortality that accompany pandemic influenza infection [14] . Pneumonia may occur as a continuum of the acute influenza syndrome when caused by the virus alone (primary pneumonia) or as a mixed viral and bacterial infection after a delay of a few days (secondary pneumonia) [28] . Identifying patients who are more likely to develop severe complications from influenza pneumonia requires a high clinical vigilance. Commonly used pneumonia severity assessment tools, such as the Pneumonia Severity Index [29] or CURB65 [30] , are not useful in deciding which patients to hospitalize in the context of primary influenza pneumonia since these tools have not been developed and validated during a pandemic scenario. Thus, careful triage in the emergency department and early identification of young patients with decreased oxygen saturation, respiratory rate above 25, concomitant diarrhea, or hypotension are crucial. Elevated lactate dehydrogenase, creatine phosphokinase, and creatinine at hospital admission may also serve as prognostic indicators of severe disease [14] . C-reactive protein and procalcitonin are increased during this acute lung injury stage of early fibroproliferation.