TABLE 2. COVID-19 attack rates among gymnasts, staff members, and household contacts associated with a SARS-CoV-2 B.1.617.2 (Delta) variant outbreak at facility A — Oklahoma, April 15–May 3, 2021.
| Group | Total no. exposed* | No. of outbreak cases,† attack rate (%) |
|---|---|---|
|
Overall
|
194
|
47 (24.2)
|
|
Gymnasts§ and staff members
|
133 |
26 (19.5) |
| Girls |
64 |
13 (20.3) |
| Girls cohort A |
12 |
0 (—) |
| Girls cohort B |
13 |
3 (23.1) |
| Girls cohort C |
6 |
1 (16.7) |
| Girls cohort D |
3 |
1 (33.3) |
| Girls cohort E |
10 |
6 (60.0) |
| Girls cohort F |
8 |
1 (12.5) |
| Girls cohort G |
12 |
1 (8.3) |
| Boys |
58 |
10 (17.2) |
| Boys cohort A |
12 |
0 (—) |
| Boys cohort B |
10 |
0 (—) |
| Boys cohort C |
6 |
3 (50.0) |
| Boys cohort D |
1 |
0 (—) |
| Boys cohort E |
3 |
1 (33.3) |
| Boys cohort F |
6 |
3 (50.0) |
| Boys cohort G |
10 |
3 (30.0) |
| Boys cohort H |
1 |
0 (—) |
| Boys cohort I |
9 |
0 (—) |
| Staff members |
11 |
3 (27.3) |
| Household contacts¶ | 80 | 42 (52.5) |
* Exposed persons were defined as gymnast cohorts and staff members identified as attending facility A, along with any household contacts of outbreak cases.
† An outbreak-associated case was defined as 1) identification of the B.1.617.2 variant based on amplicon sequencing in a person with COVID-19 with an epidemiologic link to facility A or 2) having epidemiologic linkage to a B.1.617.2 variant outbreak-associated case and classified as a confirmed or probable case per the Council of State and Territorial Epidemiologists COVID-19 Interim Case Definition, approved August 5, 2020. https://ndc.services.cdc.gov/case-definitions/coronavirus-disease-2019-2020-08-05/
§ A cohort is a group of gymnasts grouped by skill level and gender of which there were 16 in facility A. Each cohort had a designated practice schedule and had limited interaction with other cohorts within facility A.
¶ Household contacts include both outbreak-associated cases and exposed contacts from 21 of the 26 interviewed households. The remaining five households and outbreak-associated cases lost to follow-up were excluded from these numbers. Secondary cases were not identified in 14 of 21 interviewed households.