Table 4.

Number of additional people quarantined per symptomatic case under different scenarios for the absolute number of new symptomatic cases per day

	Median number of people quarantined per detected case (90% prediction interval)	Mean newly quarantined people per day assuming 20 000 new symptomatic cases per day	Mean newly quarantined people per day assuming 5000 new symptomatic cases per day	Mean newly quarantined people per day assuming 1000 new symptomatic cases per day
SI and HHQ	2 (0–4)	38 000	9400	1900
SI plus HHQ plus work or school CT	13 (1–110)	540 000	140 000	27 000
SI plus HHQ plus manual CT of acquaintances	22 (1–120)	650 000	160 000	32 000
SI plus HHQ plus manual CT of all contacts	29 (1–140)	830 000	210 000	41 000
SI plus HHQ plus app-based CT	4 (1–69)	310 000	76 000	15 000
SI plus HHQ plus manual CT of acquaintances plus app-based CT	25 (1–130)	740 000	180 000	37 000
SI plus HHQ plus manual CT of acquaintances plus limit to four daily contacts with other individuals	17 (1–110)	560 000	140 000	28 000
SI plus HHQ plus manual CT of acquaintances plus app-based CT plus limit to four daily contacts with other individuals	21 (1–110)	630 000	160 000	32 000

We assumed that quarantined contacts are independent. Estimates shown to two significant figures. If contact tracing is initiated on the basis of suspected rather than confirmed COVID-19 cases, the symptomatic case numbers here would reflect total incidence of COVID-19-like illness, which might be considerably higher than the number of confirmed cases. CT=contact tracing. HHQ=household quarantine. SI=self isolation.