Based on the common pathway theory, the shared AFgenes with influenza (CCL2, IL18, IL1B, IL6, MX1, NFKB1, RAF1, STAT1, TMPRSS2, and TNF), RA (CCL2, IL18, IL1B, IL6, MMP3, TGFB1, and TNF), and IBD (IL10, IL18, IL1B, IL6, NFKB1, NOD2, STAT1, STAT3, TGFB1, and TNF) may serve as entry points for future research on disease comorbidity mechanisms. This evidence concerns the gene NOD2 and rheumatoid arthritis.