A group from Yale University School of Medicine etc. has reported that the most dynamic unifying indicator of the pathophysiology of the new coronavirus (COVID-19) is the saliva viral load.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7805468/
Existing markers for COVID-19 include inflammatory cytokines and chemokines (CXCL10, IL-6, IL-10), inflammasome (IL-18, IL-1β), interferon (IFNα, IFNγ, IFNλ), etc.), however, they have found that the saliva virus load was very well correlated with the disease pathology. The nasopharyngeal viral load was also evaluated as a comparison. The amount of virus in saliva and nasopharyngeal (RNA copies/mL) was calculated from Ct values of RT-PCR extracting RNA from saliva. For the discrimination accuracy among non-hospitalization, moderate, severe, and deceased, strong predictive ability was obtained as follows, moderate disease (AUC = 0.96), severe disease (AUC = 0.89), and fatal (AUC = 0.91).
The upper figure of the below shows the correlation between the saliva viral load and the disease pathology, and the lower figure shows the nasopharyngeal viral load and the disease pathology.
