The present study aims to estimate the seroprevalence of brucellosis in humans attending a tertiary care hospital, King George's Medical University, Lucknow, U.P. The overall prevalence recorded in this study was 9.5% and 11.5% by anti-brucella IgM and IgG ELISA, and the study concluded that brucellosis is more frequent in explained arthritis (control) patients than unexplained arthritis (cases) patients. This evidence concerns the gene CD40LG and brucellosis.