The criteria for confirmed TBE include central nervous system (CNS) inflammation symptoms (e.g. meningitis, meningo-encephalitis, encephalomyelitis, encephaloradiculitis) and at least one of the laboratory criteria, which are either detection of the virus or its nucleic acid in a clinical specimen or detection of specific IgM and IgG antibodies in serum, seroconversion, or specific IgM in cerebrospinal fluid (CSF) [18]. This evidence concerns the gene CD40LG and meningitis.