Role of proning and positive end-expiratory pressure in COVID-19

Table 3 Histopathological features of 2009 H1N1, severe acute respiratory syndrome and severe acute respiratory syndrome coronavirus 2

Virus	Number of patients	Diffuse alveolar damage, n (%)	AFOP, n (%)	Organizing fibrosis, n (%)	End-stage fibrosis, n (%)	Superimposed pneumonia, n (%)	Microthrombi, n (%)	Pulmonary thrombosis, n (%)
2009 H1N1	287	90	0.30	40	3	30	24	6
SARS	64	98	9	47	6	31	58	28
SARS-CoV-2	171	88	4	52	1	32	57	15

AFOP: Acute fibrinous and organizing pneumonia; SARS: Severe acute respiratory syndrome; SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2.