In our study, post-COVID syndrome, accompanied by prolonged symptoms of headache, weakness, fatigue, and sleep disorders [9], is characterized by cross-correlation of MDC, IL-1b, Fractalkine, TNFa, FGF-2, EGF, IL-1RA, IFN-a2, IL-10, sCD40L, IL-8, Eotaxin, IL-12p40, and MIP-1b and a shift in the gut microbiome towards a pro-inflammatory microflora. Here, CD40LG is linked to sleep disorder.