Table. Definitions, risk assessment, mitigation strategy, and numbers of contacts traced in the COVID-19 outbreak at Bach Mai Hospital, Hanoi, Vietnam, March–April, 2020.

Group	Definition	Risk assessment	Strategy	No. tracings
F1	All patients who visited the hospital, including discharged, transferred out, and outpatients	Highest	Quarantined at centralized centers for 14 d	27,893
	Family caregivers of patients		Test for SARS-CoV-2
	Healthcare workers		Daily health assessment by healthcare workers
	Medical students and visiting scholars
	People who visited patients
	People from catering company, including nonlocal staff
	Private hired caregivers for patients
F2	Close contacts of F1	High
F3	Close contacts of F2	Medium	Isolated at home for 14 d	24,346
F4	Close contacts of F3	Low	Self-monitoring for at-risk symptoms
			Remote health monitoring by local healthcare workers