Thus, this study provides a retrospective analysis of 74 adult hospitalized patients with RSV IgM antibody positive and IgG antibody negative and 129 adult hospitalized patients with influenza A/B virus IgM antibody positive and IgG antibody negative, all presenting with lower respiratory tract infection from January 2019 to December 2020. The gene discussed is CD40LG; the disease is Recurrent lower respiratory tract infections.