Purpose: To explore the CT findings and pneumonia progression pattern of the Alpha, Delta, Omicron variants and subtypes of SARS-CoV-2 in asymptomatic patients.

Method: In this retrospective comparative study, a total of 15874 patients with COVID-19 were included: 1281 patients with wild type (748 men, 52.6 years), 7945 with Alpha variant (4972 men, 46.2), 4233 with Delta variant (2548 men) and 2415 with Omicron and subtypes (1301 man, 44.2). Chest CT evaluation included opacities and repairing changes as well as lesion distribution and laterality. Chest CT severity score was also calculated. These parameters were statistically compared across the variants.

Results: Total of 15874 patients with confirmed covid 19. Ground glass opacity (GGO), crazy paving, subpleural fibrosis with consolidation and repairing changes were calculated. Chest CT severity score was also calculated. There were 162 patients without symptoms, wild strain 12, Alpha strain 37, Delta strain 62, Omicron strain 51. Delta variant showed GGO and crazy paving with consolidation more noticeable than did the others. Wild strain had more unclear CT presentation. Alfa strain was the first strain with sharp CT presentation. Delta strain was with fast development of subpleural fibrosis. Omicron strain had smaller areas of CGO. Total lung CT severity scores were 0-5 (131), 6-10 (21), 11-15 (7), and 16 to 23 (3). There were 3 lethal cases. Post covid complication were found in 35 patients. 38 patients without symptoms were vaccinated.

Conclusions: Asymptomatic patients can have severe forms, even lethal. Post covid can be found in asymptomatic patients.