DAD is likely to be a consequence of bronchiolar obstruction and consequent hypoxia rather than direct invasion of the viruses. It is a severe pattern of lung injury and could be secondary to various pulmonary and extrapulmonary insults. 26 In this series of cases we found DAD in which alveolar collapse was prominent, differing from classic DAD found in ARF or secondary to other pulmonary and extrapulmonary insults. This finding may have important implications in the ventilation strategy of the patients. 27 In addition, the presence of intra-alveolar hemorrhage may suggest virus-associated hemophagocytic syndrome. 23 