In patients with T2DM who had recovered from COVID-19, it was demonstrated that, compared to the T2DM group before COVID-19, the detection rate of S100B increased significantly by 6.6 times (from 11.86% to 79%), and in individuals with NfT2DM after COVID-19 compared to those with NfT2DM before COVID-19—by 5.5 times (from 1.96% to 10.9%). The gene discussed is S100B; the disease is type 2 diabetes mellitus.