OBJECTIVES. To determine the proportion of peripheral blood smears with visible reactive changes in lymphocytes, monocytes and granulocyte lineage; to examine the correlation between altered morphology found in the differential blood count concerning laboratory findings of leukocytes, LDH and CRP; and to investigate whether there are differences in altered morphology concerning treatment outcomes. STUDY DESIGN. Cross-sectional study with historical data. PARTICIPANTS AND METHODS. The study included 217 patients who were hospitalized for SARS-CoV-2 infection between the onset of the pandemic and the end of 2023 at the Clinic for Infectious Diseases in Zagreb. During hospitalization, peripheral blood smears were made and values of leukocytes, C-reactive protein (CRP) and lactate dehydrogenase (LDH) were measured. Patients with HIV, hepatitis, infectious mononucleosis and hematological malignancies were excluded from the study. The blood smears were stained using the MayGrünwald-Giemsa method and analyzed by two experienced and one inexperienced observer. RESULTS. Reactive changes in lymphocytes are observed in 35% of smears and monocytic changes in 18.9%. Left shift is visible in 30.9% of subjects. Toxic granules are present in 91% of smears and Döhle bodies in 85%. At least one covicyt was found in 31.3% of subjects. Elevated leukocyte levels are present in 47% of subjects, significantly more in those where covicytes were not found. In the same group, there are significantly more patientes with the lethal outcome. Elevated CRP and LDH levels are found in the majority of subjects, more in those without covicytes, while there is no significant difference in the age of subjects, platelet levels or presence of macrothrombocytes. CONCLUSION. SARS-CoV-2 causes changes in the morphology of erythrocyte, granulocyte and platelet lineages. In one-third of samples, specific changes in lymphocyte morphology, characteristic of SARS-CoV-2 infection, are observed. The presence of these changes in peripheral blood smears is associated with a better disease outcome.