TABLE. COVID-19 testing, percentage positivity, incidence, and county hotspot status among counties with and without colleges and universities,* by instructional format on the first day of the fall 2020 semester — United States, 2020.
| Characteristic | Unmatched analysis |
Matched analysis† |
|||
|---|---|---|---|---|---|
| University counties§ |
Nonuniversity counties | University counties |
Nonuniversity counties | ||
| Remote instruction | In-person instruction | In-person instruction | |||
|
Total no. of counties
|
22
|
79
|
3,009
|
68
|
68
|
| Mean county population |
1,694,739 |
748,544 |
69,574 |
467,187 |
413,460 |
| Total no. of large colleges/universities |
31 |
84 |
— |
71 |
— |
| Mean college/university full-time enrollment in county§ |
37,769 |
27,451 |
— |
27,084 |
— |
| Mean percentage full-time college/university enrollment of total county population |
7.7 |
11.7 |
— |
13.3 |
— |
|
Percentage of counties in each urban-rural category¶
| |||||
| Large central metro |
59 |
27 |
1 |
16 |
9 |
| Large fringe metro |
9 |
13 |
12 |
13 |
32 |
| Medium metro |
18 |
28 |
11 |
32 |
28 |
| Small metro |
5 |
25 |
11 |
29 |
18 |
| Micropolitan |
9 |
8 |
21 |
9 |
9 |
| Noncore |
0 |
0 |
44 |
0 |
4 |
|
County COVID-19 testing rate per 100,000 population**
| |||||
| Mean daily rate from day –21 to day –1†† |
308 |
255.0 |
209 |
256.0 |
216 |
| Mean daily rate from day 0 to day 21 |
321 |
291.0 |
207 |
304.0 |
204 |
| Relative change, %§§ |
4.2 |
14.1 |
−1.0 |
18.8 |
–5.6 |
|
County COVID-19 RT-PCR test percentage positivity**
| |||||
| Mean from day –21 to day –1 |
8.1 |
7.8 |
8.7 |
7.5 |
8.6 |
| Mean from day 0 to day 21 |
6.4 |
8.9 |
8.0 |
9.1 |
7.9 |
| Absolute change, %§§ |
−1.8 |
1.1 |
–0.6 |
1.6 |
–0.8 |
|
County COVID-19 incidence¶¶
| |||||
| Mean incidence from day –21 to day –1 |
17.9 |
15.3 |
15.3 |
14.3 |
16.9 |
| Mean incidence from day 0 to day 21 |
14.7 |
23.9 |
14.4 |
25.5 |
13.6 |
| Relative change, %§§ |
–17.9 |
56.2 |
–5.9 |
78.3 |
–19.5 |
|
County COVID-19 hotspot activity ***
| |||||
| Percentage detected as a hotspot from day –21 to day –1 |
9.1 |
8.9 |
4.4 |
8.8 |
13.2 |
| Percentage detected as a hotspot from day 0 to day 21 |
18.2 |
39.2 |
5.9 |
42.6 |
14.7 |
| Absolute change, %§§ | 9.1 | 30.4 | 1.5 | 33.8 | 1.5 |
Abbreviations: COVID-19 = coronavirus disease 2019; RT-PCR = reverse transcription–polymerase chain reaction.
* 133 counties had institutions of higher education (large colleges or universities). Some counties (n = 32; 24%) opened on or after August 29 and were excluded from analysis. University counties are defined as counties with a large college or university. Nonuniversity counties are defined as counties without a large college or university.
† University counties matched to geographically proximate comparison counties with similar population size. Matches for each university county were identified by first listing all candidate (county) matches without large colleges and universities (nonuniversity counties) that had a similar population size (± 30%) and that were located within 500 miles (805 km) of each university county. From these candidate matches the final match was selected based on closest proximity. After matching, the average distance between counties in matched university county and nonuniversity county pairs was 114 miles (183 km) with a maximum distance of 471 miles (758 km).
§ Colleges and universities were included in the analysis if they had ≥20,000 total enrolled students, which included full-time and part-time students. The full-time student enrollments from these included institutions were combined across each university county. The number of full-time student enrollments in the university counties ranged from 11,774 to 192,173.
¶ Urban-rural classifications are from the National Center for Health Statistics’ six-level urban-rural classification scheme for U.S. counties (https://www.cdc.gov/nchs/data_access/urban_rural.htm).
** Testing rates and percentage positivity for reverse transcription–polymerase chain reaction tests were obtained from COVID-19 electronic laboratory reporting data submitted by state health departments and from data submitted directly by public health, commercial, and reference laboratories.
†† Day –21, –1, and 21 are relative to day 0, which indicates the start date of instruction at colleges and universities for the fall 2020 semester. The nonuniversity counties were assigned the median start date in the unmatched analysis and were assigned the start date of their matched university county counterpart in the matched analysis.
§§ Absolute differences are described for percentage-based measures (i.e., test positivity and hotspot detection) and relative changes described for rate-based measures (i.e., testing rate and incidence).
¶¶ Incidence (cases per 100,000) was calculated using daily reported COVID-19 case-counts from state and county health department websites compiled by USAFacts (https://usafacts.org/).
*** Hotspot, or rapid riser, counties met all four of the following criteria, relative to the date assessed: 1) >100 new COVID-19 cases in the most recent 7 days; 2) an increase in the most recent 7-day COVID-19 incidence over the preceding 7-day incidence; 3) a decrease of no more than 60% or an increase in the most recent 3-day COVID-19 incidence over the preceding 3-day incidence; and 4) a ratio of 7-day incidence to 30-day incidence exceeding 0.31. In addition to those four criteria, hotspots met at least one of the following criteria: 1) >60% change in the most recent 3-day COVID-19 incidence or 2) >60% change in the most recent 7-day incidence.