The more transmissible and dangerous Delta variant of COVID-19 now accounts for nearly all cases of the disease in Colorado and has been confirmed in most counties, with updated data showing the variant making big gains since late last month.

According to August 13 statistics from the Colorado Department of Public Health and Environment, the Delta variant accounted for an overwhelming 98.98 percent of COVID-19 infections in the state for the week of July 25, the most recent for which numbers are available. The presence of the variant has been confirmed in 51 of 64 counties, and the thirteen exceptions (Baca, Cheyenne, Clear Creek, Costilla, Crowley, Dolores, Hinsdale, Jackson, Kiowa, Lincoln, Mineral, Phillips and San Juan) are, in general, lightly populated places where the scarcity of resources can lead to incomplete reporting.

On June 23, La Plata County had no registered Delta variant cases; it had 42 as of August 13. Delta County went from none in June to 24, and Routt County now has 28 cases — 27 more than on June 23.

As of July 30, thirteen Colorado counties exceeded fifty confirmed Delta variant cases. Now Summit County has joined the club, with 58 cases (it had none on June 23). And the case counts have gone way up in the others, more than doubling over the previous fourteen days in Denver (from 66 to 138) and Pueblo (from 50 to 104).

Mesa County, anchored by Grand Junction, continues to have the most Delta variant cases in Colorado, and now registers 1,026. But El Paso County, home of Colorado Springs, is catching up fast, owing to a steady progression of Delta variant infections: 103 on June 23, 237 on July 2, 543 on July 30, and 784 today.

Here are the fourteen Colorado counties with at least fifty confirmed Delta variant cases as of August 13, listed from smallest counts to largest, and including cases from June 23, July 2 and July 30.

Summit
0 Delta variant cases on June 23
1 Delta variant case on July 2
58 Delta variant cases on August 12

Pueblo
0 Delta variant cases on June 23
10 Delta variant cases on July 2
50 Delta variant cases on July 30
104 Delta variant cases on August 12

Larimer
2 Delta variant cases on June 23
9 Delta variant cases on July 2
58 Delta variant cases on July 30
105 Delta variant cases on August 12

Denver
6 Delta variant cases on June 23
10 Delta variant cases on July 2
66 Delta variant cases on July 30
138 Delta variant cases on August 12

Weld
6 Delta variant cases on June 23
13 Delta variant cases on July 2
74 Delta variant cases on July 30
136 Delta variant cases on August 12

Adams
10 Delta variant cases on June 23
19 Delta variant cases on July 2
86 Delta variant cases on July 30
170 Delta variant cases on August 12

Douglas
20 Delta variant cases on June 23
28 Delta variant cases on July 2
87 Delta variant cases on July 30
153 Delta variant cases on August 12

Boulder
12 Delta variant cases on June 23
16 Delta variant cases on July 2
105 Delta variant cases on July 30
169 Delta variant cases on August 12

Moffat
18 Delta variant cases on June 23
40 Delta variant cases on July 2
107 Delta variant cases on July 30
117 Delta variant cases on August 12

Garfield
27 Delta variant cases on June 23
44 Delta variant cases on July 2
108 Delta variant cases on July 30
133 Delta variant cases on August 12

Jefferson
2 Delta variant cases on June 23
17 Delta variant cases on July 2
109 Delta variant cases on July 30
198 Delta variant cases on August 12

Arapahoe
12 Delta variant cases on June 23
30 Delta variant cases on July 2
165 Delta variant cases on July 30
261 Delta variant cases on August 12

El Paso
103 Delta variant cases on June 23
237 Delta variant cases on July 2
543 Delta variant cases on July 30
784 Delta variant cases on August 12

Mesa
218 Delta variant cases on June 23
418 Delta variant cases on July 2
890 Delta variant cases on July 30
1,026 Delta variant cases on August 12