CD40LG and Epstein-Barr virus infection: Two additional long-term long COVID-19 patients were positive for EBV VCA IgM but not EBV EA-D IgG, and the two patients positive for EBV reactivation in the long-term control group were positive for EBV EA-D IgG only, they caught more cases of EBV reactivation by EBV EA-D IgG, while we only used EBV VCA IgM in the detection of EBV infection.