In the case of tularemia, also humoral immune responses, which are important for diagnosis, are unusually long-lasting, e.g., elevated IgM antibodies have been reported to be present 11 years after infection and low, but significant IgG antibody titers detectable in 50% of individuals up to 25 years after infection (Koskela and Salminen, 1985; Ericsson et al., 1994; Maurin, 2020). This evidence concerns the gene CD40LG and tularemia.