The most ominous cases are those infections that progress rapidly to ARDS and multilobar alveolar opacification. These patients usually present with gradually increasing dyspnea and severe hypoxemia after an antecedent of 2 to 5 days of typical influenza symptoms [14] . The cough is usually productive of thin, often bloody, sputum with few cells. Hypoxemia increases progressively to the point of respiratory failure requiring intubation and mechanical ventilation, often after only one day of hospitalization [14] .