A cross-sectional study conducted on 288 stored plasma samples collected before COVID-19 (in 2017–2018) in Cameroon, found cross-reactive antibodies to SARS-CoV-2 in 13.5% of samples, of which 7.3% was IgG, 7.3% IgM, and 1.0% IgG/IgM [136]. This evidence concerns the gene CD40LG and COVID-19.