FIG 2.
Morning viral loads are significantly higher than evening viral loads during most of SARS-CoV-2 infection. (A and B) The difference in N1 CT values (ΔCT) in 703 morning-to-evening and evening-to-morning successive saliva specimen pairs (A) and 365 morning-to-evening and evening-to-morning successive nasal swab specimen pairs (B), plotted relative to symptom onset. One point in panel A and one point in panel B had ΔCT values outside the y axis of the plot; these are represented as black stars at −15. (C and D) The difference in N1 CT values in 703 morning-to-evening and evening-to-morning sequential saliva (C) and nasal swab (D) specimen pairs relative to symptom onset. Morning-to-evening or evening-to-morning ΔCT values were then binned into presymptomatic or 4-day infection stages. The distributions of morning-to-evening and evening-to-morning ΔCT values for each infection stage bin were then statistically compared using the Wilcoxon matched-pair signed-rank test; ns, nonsignificant or insufficient data points to perform analysis; *, P < 0.05; **, P < 0.01; ****, P < 0.001. Black lines indicate average viral load. ND, not detected.