2. Lungs Hepatization, severe lung consolidation, edema with pleural effusion, mucopurulent material in the tracheobronchial tree, focal hemorrhage, alveolar and septal fibrosis, edema, alveolar hemorrhage, fibrin exudation in alveolar spaces, hyaline membrane formation, and extreme bronchiolar injury indicate the acute phase. Acute respiratory distress syndrome, septic shock, the mild upper respiratory illness may result in swiftly growing pneumonitis, respiratory failure Severe acute respiratory syndrome (SARS), acute respiratory distress syndrome (ARDS), focal reactive hyperplasia of pneumocytes with patchy inflammatory cellular infiltration, edema, multinucleated giant cells, protruding hyaline membranes, and proteinaceous exudate.