Table 1.

Illinois risk classification of health-care personnel and community contacts with potential exposure to COVID-19

	Community contacts			Health-care personnel contacts
	Type of exposure	Example	Public health measure	Type of exposure	Example	Public health measure
High-risk contacts	Living in the same household as, being an intimate partner of, or providing care in a non-health-care setting (such as a home) for a person with symptomatic laboratory-confirmed COVID-19	Domestic partner	Home quarantine for 14 days after last exposure*; active symptom monitoring for 14 days after last exposure	Performing or being present in the room for a procedure likely to generate higher concentrations of respiratory secretions or aerosols while not using all recommended PPE†, or close contact while not wearing respiratory protection with a patient with laboratory-confirmed COVID-19 infection who was not wearing a facemask	Health-care personnel not wearing all recommended PPE who collected or were present for the collection of nasopharyngeal or oropharyngeal specimens‡	Home quarantine*; exclude from work; active symptom monitoring for 14 days after last exposure
Medium-high-risk contacts	Prolonged or frequent contact with a person with symptomatic laboratory-confirmed COVID-19§	Family members visited for prolonged periods or close work associates	Home quarantine for 14 days after last exposure*; active symptom monitoring for 14 days after last exposure	Prolonged (15 min or more) contact with a patient with laboratory-confirmed COVID-19 infection or their secretions or excretions while not using all recommended PPE†	Performing a check of the vital signs and phlebotomy on a masked patient while wearing gloves and a surgical mask	Exclude from work; active symptom monitoring for 14 days after last exposure
Medium-risk contacts	Close contact with a person with symptomatic laboratory-confirmed COVID-19 and not having any exposures that meet a high-risk or medium-high-risk definition	Colleagues who work less closely together but still have regular face-to-face contact	Active symptom monitoring for 14 days after last exposure	More than brief contact (>1–2 min) with a patient with laboratory-confirmed COVID-19 infection or their secretions or excretions while not using all recommended PPE† that does not meet a high-risk or medium-high-risk definition	Examined patient for 5 min while wearing mask, gown, gloves, and faceshield (but no respirator)	Exclude from work; active symptom monitoring for 14 days after last exposure
Low-risk contacts	Being in the same indoor environment with (or within 2 h of) a person with symptomatic laboratory-confirmed COVID-19	Shared a hospital or outpatient waiting room or entered space within 2 h of a case	Active symptom monitoring for 14 days after last exposure	Any duration of contact with a patient with laboratory-confirmed COVID-19 while using all recommended PPE†, brief interaction with the patient (1–2 min) not involving direct contact while not using all recommended PPE†, or working at the same time and location as a confirmed case but unsure whether they were in the same room	Examined patient while wearing gloves, gown, faceshield, or goggles and appropriate, fit-tested respiratory protection; entered patient’s room briefly to bring the patient a drink but did not have direct contact with the patient or their secretions or excretions	Active symptom monitoring for 14 days after last exposure
Non-contacts	Interactions with a person with symptomatic laboratory-confirmed COVID-19 that do not meet high-risk, medium-high-risk, medium-risk, or low-risk conditions	Walking by a patient in a corridor	None	Did not meet any of the high-risk, medium-high-risk, medium-risk, or low-risk conditions	Walking by a patient in a corridor	None

COVID-19=coronavirus disease 2019. PPE=personal protective equipment. CDC=US Centers for Disease Control and Prevention. MERS-CoV=Middle East respiratory syndrome coronavirus.

^*Implemented after identification of the second case of laboratory-confirmed COVID-19 in Illinois on Jan 30, 2020.

^†Recommended PPE includes respiratory protection (ie, respirator), goggles or faceshield that covers the front and sides of face, gloves, and a gown.

^‡Risk categorisation was developed on Jan 26, 2020, before published guidance from CDC for COVID-19.¹⁰ Criteria were based on published MERS-CoV guidance and additional input from CDC subject matter experts. Close contact was defined as being within approximately 6 feet or within the room or care area of a confirmed COVID-19 case (including sharing a health-care waiting area or room), or being in a shared air space vacated by a confirmed case within the previous 2 h. Transient interactions, such as walking by confirmed case, were not considered close contact. Of note, nasopharyngeal and oropharyngeal specimen collection were not listed as aerosol-generating procedures in the CDC guidance, but were included as high-risk exposures in this investigation.

^§Risk categorisation was developed on Jan 31, 2020, before published guidance from CDC for COVID-19.¹¹ Criteria were based on published MERS-CoV guidance and additional input from CDC and state and local health officials. The medium-high-risk classification was included owing to the identification of some community contacts who did not meet the highest category of exposure risk but were nevertheless concerning.