Table 4.

Proportion of nasal swabs PCR positive, and mean Ct values in PCR positive swabs by time since onset of symptoms in infected contacts and index cases; first and second nasal swab combined.

interval from symptom onset	PCR Positive	Total tested	% PCR Positive (95% CI)	mean Ct
−7 to −1	2	11	18.2% (2.3–51.8)	23.22
0 to 2	11	21	52.4% (29.8–74.3)	27.34
3 to 6	35	56	62.5% (48.5–75.1)	27.33
7 to 9	45	85	52.9% (41.8–63.9)	30.02
10 to 13	37	128	28.9% (21.2–37.6)	32.95
14 to 20	27	197	13.7% (9.2–19.3)	34.88
21 to 27	4	71	5.6% (1.6–13.8)	36.35
28+	3	34	8.8% (1.9–23.7)	36.51
Total	164	603	27.2% (23.7–3u0.9)	30.94

*95% CI does not account for some individuals contributing two samples.