Purpose: To explore the CT findings and pneumonia progression pattern of the wild strain, Alpha, Delta, Omicron variants and subtypes of SARS-CoV-2 and to compare findings with long covid findings.

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 ground glass opacity, crazy paving, consolidation, and fibrosis. These parameters were statistically compared across the variants in patients with long covid. We performed CT examination in all patients in acute illness and in 5981 with long covid. MR of abdomen, heart, and other parts, according to symptoms.

Results: Ground glass opacity (GGO), crazy paving, subpleural fibrosis with consolidation and repairing changes were found in 13993 patients. Lung changes, most fibrosis, were found in 1001 patients with long covid. Different problems with heart muscle were found in 782 patients. Changes in blood vessels were found in 465 patients. Subpleural fibrosis was more often after Delta strain, problems with heart was more often after Alpha strain. Problems with blood vessels was more often in patients with severity score lower than 10. Muscle problems were more often after Omicron strain. Microischemia in brain were more often in Alpha strain.

Conclusions: It is possible to predict long covid in patient with early subpleural fibrosis. Patients with chronic fatigue syndrome were often with Omicron strain.