Table 1. Estimates for the incubation period based on the Weibull distribution for the COVID-19 epidemic, by age group, sex, epidemic phase and location, China, 1 January–11 February 2020 (n = 1,158).

Incubation period (days)	Number of cases	Median		95th percentile		99th percentile
Incubation period (days)	Number of cases	Estimate	95% CI^a	Estimate	95% CI^a	Estimate	95% CI^a
Age^b(years)
< 18	61	8.8	7.3–10.5	18.0	14.8–20.8	22.3	16.8–25.4
18‒44	500	7.1	6.7–7.6	14.5	13.6–15.3	17.8	16.1–19.2
45‒59	334	6.9	6.4–7.4	14.3	13.2–15.4	17.8	15.7–19.3
≥ 60	193	7.2	6.4–8.0	15.6	14.0–17.2	19.6	16.6–22.2
Sex^b
Female	568	7.3	6.8–7.7	15.2	14.2–16.1	18.9	17.2–20.4
Male	587	7.1	6.7–7.5	14.9	14.0–15.8	18.5	16.9–20.0
Location
South	640	7.0	6.6–7.4	14.8	14.0–15.7	18.5	17.0–20.0
North	518	7.4	6.9–7.9	15.3	14.4–16.3	19.0	17.2–20.4
Phase
Before 25 Jan 2020	278	4.4	4.0–4.9	10.8	9.6–11.8	14.0	11.9–15.8
25‒31 Jan 2020	543	6.5	6.1–6.8	12.2	11.5–12.8	14.7	13.5–15.7
After 31 Jan 2020	337	11.5	11.1–12.0	17.1	16.3–17.8	19.2	18.1–20.2
Overall	1,158	7.2	6.9–7.5	15.1	14.4–15.7	18.7	17.6–19.8

CI: confidence interval; COVID-19: coronavirus disease.

^a 95% CI was calculated using 1,000 parametric bootstrap samples.

^bAge and sex data were not available for 70 and three cases, respectively.