The ultrastructural features were represented by bronchial and alveolar epithelium necrosis, a destroyed alveolar epithelium/basement membrane unity and the presence of viral-like particles (Table 3) . Patients 3 and 5 presented more prominent changes at submicroscopic level. Cytoplasmic swelling, necrosis, and degenerative changes of the endoplasmic reticulum and other organelles were present in bronchial and AECs (Figure 2A-C) . A large number of bronchiolar and AECs were detached from the basement membrane and were showing apoptosis (Figure 2A, B) . Lymphocytes also exhibited apoptosis. Sloughing of apoptotic bronchiolar cells and AECs causing denudation of the epithelial basement membrane was followed by deposition of hyaline membranes ( Figure 2D ).