According to a paper published yesterday[1], the pre-symptomatic period is about 2.3 days[2]. [1] https://www.nature.com/articles/s41591-020-0869-5 https://www

According to a paper published yesterday[1], the pre-symptomatic period is about 2.3 days[2]. [1] https://www.nature.com/articles/s41591-020-0869-5 https://www.nature.com/articles/s41591-020-0869-5 [2] "we inferred that infectiousness started from 2.3 days (95% CI, 0.8–3.0 days) before symptom onset and peaked at 0.7 days (95% CI, −0.2–2.0 days) before symptom onset "