CD40LG and Epstein-Barr virus infection: The prevalence of VCA-IgM, as a parameter of acute EBV infection, was 14.6%, 10.2%, 10.4%, 6.3% and 3.1% in patients aged under 5 years, 6–10 years,11–20 years, 21–30 years, 31–40 years old, respectively, and decreased to 2%~3% in older patients.