The Delta variant continues to be the dominant COVID-19 strain in Colorado, and has now been confirmed in sixty of the state's 64 counties. And while Mesa County, on the Western Slope, has been the variant's epicenter for months, it's now been surpassed by El Paso County, Colorado's most populous county, according to the 2020 Census.

The size of El Paso County, which is anchored by Colorado Springs, offers even more opportunities for the Delta variant to spread — and that's also true for three sublineages of the strain, collectively known as Delta Plus, which are also growing at a concerning clip.

The Colorado Department of Public Health and Environment calculates that for the week of August 15, the most recent for which statistics are available, the Delta variant was responsible for 89.09 percent of positive cases in the state, followed by 1.82 percent Delta Plus 1 (scientific name: AY.1), 5.45 percent for Delta Plus 3 (AY.3), 1.82 percent for Alpha, the original strain, and 1.82 percent for other strains. For this particular seven-day period, the CDPHE puts the percentage of Delta Plus 2 (AY.3) and Gamma cases at zero.

The state health department also offers breakdowns of the various strains for every Colorado county, and lists the four with no confirmed Delta variant cases right now: Baca, Costilla, Kiowa and Jackson. The numbers from yesterday, August 31, reveal the number of infections sequenced by researchers to confirm strains, not every case — but the totals still offer an indication of where the Delta variant is most prevalent. Mesa is the only county in the top ten from the western half of the state — and Denver has fewer cases than two other counties in the greater metro area. Here's the rundown:

1. El Paso: 1,413
2. Mesa: 1,138
3. Arapahoe: 626
4. Adams: 421
5. Denver: 411
6. Boulder: 374
7. Douglas: 315
8. Weld: 267
9. Larimer: 239
10. Jefferson: 223

Of the assorted Delta Plus strains, which researchers are studying to determine if they're any more or less dangerous than the first Delta variant, Delta Plus 3 pops up most often. The counties with the highest number of Delta variant cases often have the most Delta Plus 3 infections, but there are exceptions. For instance, El Paso is the current Delta Plus 3 leader, with seventy cases; thus far, only eight have been found in Mesa County. The other counties with double-digit Delta Plus 3 cases are Denver (39), Jefferson (36), Adams (35), Arapahoe (34), Larimer (32), Weld (21), Douglas (18), Boulder (14), Garfield (14), Pueblo (13) and La Plata (10).

Here are the COVID-19 strain case counts for the sixty Colorado counties with at least one Delta variant case, listed in alphabetical order.

Adams County
Alpha: 1,162
Beta: 4
Gamma: 172
Delta: 421
Delta Plus 1: 1
Delta Plus 2: 0
Delta Plus  3: 35

Alamosa County
Alpha: 33
Beta: 0
Gamma: 2
Delta: 18
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 6

Arapahoe County
Alpha: 1,375
Beta: 10
Gamma: 169
Delta: 626
Delta Plus 1: 0
Delta Plus 2: 5
Delta Plus 3: 34

Archuleta County
Alpha: 35
Beta: 0
Gamma: 1
Delta: 65
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 3

Bent County
Alpha: 3
Beta: 0
Gamma: 2
Delta: 4
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Boulder County
Alpha: 714
Beta: 0
Gamma: 44
Delta: 374
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 14

Broomfield County
Alpha: 123
Beta: 0
Gamma: 20
Delta: 63
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 4

Chaffee County
Alpha: 38
Beta: 15
Gamma: 0
Delta: 14
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 2

Cheyenne County
Alpha: 0
Beta: 0
Gamma: 0
Delta: 1
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Clear Creek County
Alpha: 1
Beta: 0
Gamma: 1
Delta: 7
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Conejos County
Alpha: 22
Beta: 0
Gamma: 0
Delta: 30
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 2

Crowley County
Alpha: 5
Beta: 0
Gamma: 0
Delta: 2
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Custer County
Alpha: 3
Beta: 0
Gamma: 1
Delta: 3
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Delta County
Alpha: 15
Beta: 0
Gamma: 13
Delta: 32
Delta Plus 1: 0
Delta Plus 2: 1
Delta Plus 3: 1

Denver County
Alpha: 1,146
Beta: 6
Gamma: 230
Delta: 411
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 39

Dolores County
Alpha: 4
Beta: 0
Gamma: 0
Delta: 1
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Douglas County
Alpha: 1,081
Beta: 4
Gamma: 86
Delta: 315
Delta Plus 1: 0
Delta Plus 2: 1
Delta Plus 3: 18

Eagle County
Alpha: 67
Beta: 0
Gamma: 30
Delta: 37
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 3

El Paso County
Alpha: 2,955
Beta: 2
Gamma: 181
Delta: 1,413
Delta Plus 1: 0
Delta Plus 2: 8
Delta Plus 3: 70

Elbert County
Alpha: 45
Beta: 0
Gamma: 0
Delta: 22
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Fremont County
Alpha: 174
Beta: 0
Gamma: 10
Delta: 68
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Garfield County
Alpha: 185
Beta: 0
Gamma: 19
Delta: 206
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 14

Gilpin County
Alpha: 10
Beta: 0
Gamma: 1
Delta: 6
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Grand County
Alpha: 17
Beta: 0
Gamma: 6
Delta: 18
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Gunnison County
Alpha: 30
Beta: 0
Gamma: 18
Delta: 32
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Hinsdale County
Alpha: 0
Beta: 0
Gamma: 0
Delta: 1
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Huerfano County
Alpha: 20
Beta: 0
Gamma: 1
Delta: 4
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Jefferson County
Alpha: 954
Beta: 11
Gamma: 223
Delta: 411
Delta Plus 1: 0
Delta Plus 2: 1
Delta Plus 3: 36

Kit Carson County
Alpha: 1
Beta: 0
Gamma: 0
Delta: 3
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

La Plata County
Alpha: 272
Beta: 0
Gamma: 16
Delta: 85
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 10

Lake County
Alpha: 4
Beta: 0
Gamma: 0
Delta: 5
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Larimer County
Alpha: 992
Beta: 0
Gamma: 69
Delta: 239
Delta Plus 1: 0
Delta Plus 2: 1
Delta Plus 3: 32

Las Animas County
Alpha: 9
Beta: 1
Gamma: 0
Delta: 50
Delta Plus 1: 0
Delta Plus 2: 3
Delta Plus 3: 4

Lincoln County
Alpha: 1
Beta: 0
Gamma: 0
Delta: 2
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Logan County
Alpha: 16
Beta: 0
Gamma: 3
Delta: 12
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 2

Mesa County
Alpha: 320
Beta: 0
Gamma: 53
Delta: 1,138
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 8

Mineral County
Alpha: 3
Beta: 0
Gamma: 0
Delta: 2
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Moffat County
Alpha: 5
Beta: 6
Gamma: 15
Delta: 169
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Montezuma County
Alpha: 56
Beta: 0
Gamma: 5
Delta: 29
Delta Plus 1: 0
Delta Plus 2: 1
Delta Plus 3: 2

Montrose County
Alpha: 52
Beta: 0
Gamma: 6
Delta: 73
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 4

Morgan County
Alpha: 31
Beta: 0
Gamma: 3
Delta: 4
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Otero County
Alpha: 16
Beta: 0
Gamma: 0
Delta: 7
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Ouray County
Alpha: 2
Beta: 0
Gamma: 2
Delta: 5
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 2

Park County
Alpha: 28
Beta: 0
Gamma: 2
Delta: 11
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Phillips County
Alpha: 2
Beta: 0
Gamma: 0
Delta: 1
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Pitkin County
Alpha: 105
Beta: 0
Gamma: 47
Delta: 40
Delta Plus 1: 0
Delta Plus 2: 1
Delta Plus 3: 3

Prowers County
Alpha: 10
Beta: 0
Gamma: 0
Delta: 1
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Pueblo County
Alpha: 623
Beta: 1
Gamma: 39
Delta: 192
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 13

Rio Blanco County
Alpha: 16
Beta: 0
Gamma: 20
Delta: 45
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 4

Rio Grande County
Alpha: 14
Beta: 0
Gamma: 0
Delta: 11
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Routt County
Alpha: 43
Beta: 0
Gamma: 19
Delta: 48
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Saguache County
Alpha: 4
Beta: 0
Gamma: 1
Delta: 10
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

San Juan County
Alpha: 1
Beta: 0
Gamma: 0
Delta: 9
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 2

San Miguel County
Alpha: 8
Beta: 0
Gamma: 0
Delta: 9
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Sedgwick County
Alpha: 5
Beta: 2
Gamma: 0
Delta: 4
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 2

Summit County
Alpha: 146
Beta: 0
Gamma: 16
Delta: 160
Delta Plus 1: 1
Delta Plus 2: 0
Delta Plus 3: 1

Teller County
Alpha: 67
Beta: 1
Gamma: 6
Delta: 11
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0

Washington County
Alpha: 1
Beta: 0
Gamma: 0
Delta: 2
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 1

Weld County
Alpha: 1,016
Beta: 0
Gamma: 41
Delta: 267
Delta Plus 1: 1
Delta Plus 2: 0
Delta Plus 3: 21

Yuma County
Alpha: 1
Beta: 0
Gamma: 1
Delta: 4
Delta Plus 1: 0
Delta Plus 2: 0
Delta Plus 3: 0