Owing to technical limitations in obtaining the MAT (the Ministry of Health of Ukraine suspended all high-threat live pathogen work after the start of the military conflict in Ukraine), the diagnosis of leptospirosis was confirmed on day 7 with an ELISA assay (SERION ELISA classic Leptospira IgM): increased titer of IgM antibodies (0.556 IgM) to Leptospira interrogans, reference negative values of IgM in this test system was <0.38. This evidence concerns the gene CD40LG and leptospirosis.