TABLE 1. Characteristics of index and school-associated patients with laboratory-confirmed COVID-19 in 20 elementary schools — Salt Lake County, Utah, December 3, 2020–January 31, 2021.

Characteristic	No. (%) of persons with COVID-19
	Index (n = 51)*	School-associated (n = 5)†
Cases per school, median (range)	2 (1–9)	0 (0–2)
School contacts, median (range)	20 (5–53)	—§
Close contacts, median (range)	6 (0–23)	—
Other school contacts, median (range)	13 (0–52)	—
Median age, yrs (range)
Students (index: n = 40; school-associated: n = 4)	9.5 (5–12)	10.5 (10–12)
Staff members (index: n = 11; school-associated: n = 1)	50 (26–62)	43 (43–43)
Sex
Male	24 (47.1)	2 (40.0)
Female	27 (52.9)	3 (60.0)
Race/Ethnicity
White, non-Hispanic	30 (58.8)	1 (20.0)
Hispanic/Latino	15 (29.4)	2 (40.0)
Black/African American	1 (2.0)	0 (0.0)
Asian	1 (2.0)	1 (20.0)
Native Hawaiian/Other Pacific Islander	2 (3.9)	0 (0.0)
American Indian or Alaska Native	0 (0.0)	0 (0.0)
Multiracial	2 (3.9)	1 (20.0)
Grade in school¶
Kindergarten	5 (12.5)	0 (0.0)
1	3 (7.5)	0 (0.0)
2	2 (5.0)	0 (0.0)
3	6 (15.0)	0 (0.0)
4	6 (15.0)	2 (50.0)
5	8 (20.0)	0 (0.0)
6	10 (25.0)	2 (50.0)
Role in school
Students	40 (78.4)	4 (80.0)
Head teachers	6 (11.8)	1 (20.0)
Paraeducators**	0 (0.0)	0 (0.0)
Other teachers††	4 (7.8)	0 (0.0)
Other staff members§§	1 (2.0)	0 (0.0)
Days in school while infectious, median (range)	2 (1–4)	0 (0–2)
Symptom status
Ever symptomatic	35 (68.6)	2 (40.0)
Asymptomatic	16 (31.4)	3 (60.0)
One or more underlying medical condition¶¶	9 (20.9)	0 (0.0)
Quarantine status after exposure to index patient***
Under quarantine	—	3 (60.0)
Notified, close contact	—	0 (0.0)
Notified, not close contact	—	2 (40.0)

Abbreviation: IQR= interquartile range.

* An index patient was defined as a student or staff member with laboratory-confirmed SARS-CoV-2 infection who had attended in-person school while infectious for at least 1 day. Infectious period was estimated as 2 days before to 10 days after symptom onset (if symptomatic) or first positive specimen collection date (if asymptomatic).

^† School-associated transmission was excluded if 1) the school contact had an illness onset (if symptomatic, symptom onset, if asymptomatic, first positive test date) before the last date of school exposure, 2) a household member had an illness onset (if symptomatic, symptom onset, if asymptomatic, first positive test date) within 14 days of the positive school contact’s illness onset (if school contact was symptomatic) or before the last date of school exposure (if the school contact was asymptomatic) or 3) whole genome sequencing supported nonschool-associated transmission.

^§ Dashes indicate that data are not applicable.

^¶ Restricted to students. For index patients, n = 40, for secondary cases, n = 4.

** Includes teacher aides and interns.

^†† Includes ethics teachers, instructional coaches, learning support teachers, special education teachers, and substitute teachers.

^§§ Includes administrators, bus drivers, and health specialists.

^¶¶ Missing data: Underlying medical conditions: eight index patients, one school-associated patient.

*** Starting January 4, 2021, the school district changed its quarantine policy based on changes to state recommendations, and only students and staff members identified as close contacts (i.e., within 6 ft of the index patient for a cumulative total of ≥15 minutes over a 24-hour period) of the index patient were quarantined when both were maskless; previously, all close contacts would have been quarantined regardless of mask use. Any close contacts identified in January who met the criteria to not quarantine were categorized as “Notified, close contact.” Those who shared a classroom space with the index patient but were not identified as close contacts were categorized as “Notified, not close contact.”