In the overwhelming majority of cases where a serological follow-up was possible, no IgM-IgG seroconversion was observed; as exemplified in a large cohort of professional football players in Germany where 2.3% of positive IgM athletes with neither clinical Lyme disease nor seroconversion was observed in the follow-up (Breitbart et al., 2019). This evidence concerns the gene CD40LG and Lyme disease.