CD40LG and tick-borne encephalitis: In 2020, 3817 cases of TBE were reported (97.8% confirmed mainly by the detection of specific IgM and IgG antibodies in serum and cerebrospinal fluid, usually by enzyme-linked immunosorbent assay, and some after which a TBEV-specific virus neutralization test was applied) in 24 countries of the EU/EEA, with a clear seasonal pattern (95% of TBE human cases occurring between May and November and 5% between December and April) [32].