For influenza diagnosis, six studies [14,21,23,24,25,26] used PCR alone, one study [11] used enzyme-linked immunosorbent assay (ELISA) immunoglobulin M (IgM) alone, one study [20] used ELISA IgM/IgG/PCR, and two studies [13,22] did not specify the diagnostic method (Table 1). The gene discussed is CD40LG; the disease is influenza.