| County | Reported* | Tested | Positive | % Tested Positive |
| Alameda | 706 | 128 | 12 | 9% |
| Alpine | 3 | - | - | - |
| Amador | 110 | 25 | 3 | 12% |
| Butte | 751 | 139 | 38 | 27% |
| Calaveras | 129 | 28 | 1 | 4% |
| Colusa | 46 | 7 | 3 | 43% |
| Contra Costa | 2227 | 317 | 88 | 28% |
| Del Norte | 27 | 2 | 1 | 50% |
| El Dorado | 543 | 89 | 9 | 10% |
| Fresno | 1232 | 175 | 44 | 25% |
| Glenn | 92 | 37 | 17 | 46% |
| Humboldt | 78 | 6 | 1 | 17% |
| Imperial | 35 | - | - | - |
| Inyo | 35 | 7 | - | - |
| Kern | 1590 | 193 | 10 | 5% |
| Kings | 133 | 10 | 1 | 10% |
| Lake | 94 | 11 | 2 | 18% |
| Lassen | 23 | 3 | - | - |
| Los Angeles | 5535 | 909 | 478 | 53% |
| Madera | 121 | 29 | 3 | 10% |
| Marin | 219 | 28 | 1 | 4% |
| Mariposa | 18 | 4 | - | - |
| Mendocino | 79 | 16 | 1 | 6% |
| Merced | 207 | 32 | 5 | 16% |
| Modoc | 17 | 2 | 1 | 50% |
| Mono | 11 | 3 | 2 | 67% |
| Monterey | 272 | 44 | 6 | 14% |
| Napa | 88 | 3 | 1 | 33% |
| Nevada | 305 | 59 | 5 | 8% |
| Orange | 2996 | 922 | 624 | 68% |
| Placer | 724 | 18 | 4 | 22% |
| Plumas | 57 | 16 | - | - |
| Riverside | 1269 | 89 | 39 | 44% |
| Sacramento | 3106 | 420 | 130 | 31% |
| San Benito | 34 | 4 | - | - |
| San Bernardino | 1554 | 326 | 175 | 54% |
| San Diego | 1742 | 787 | 551 | 70% |
| San Francisco | 105 | 14 | - | - |
| San Joaquin | 1509 | 202 | 69 | 34% |
| San Luis Obispo | 180 | 28 | 2 | 7% |
| San Mateo | 389 | 73 | 2 | 3% |
| Santa Barbara | 96 | 15 | 1 | 7% |
| Santa Clara | 961 | 84 | 11 | 13% |
| Santa Cruz | 163 | 30 | 3 | 10% |
| Shasta | 406 | 20 | 7 | 35% |
| Sierra | 16 | 1 | - | - |
| Siskiyou | 21 | 3 | - | - |
| Solano | 542 | 20 | 7 | 35% |
| Sonoma | 495 | 93 | 11 | 12% |
| Stanislaus | 938 | 128 | 45 | 35% |
| Sutter | 179 | 8 | 2 | 25% |
| Tehama | 137 | 31 | 6 | 19% |
| Trinity | 14 | 3 | 1 | 33% |
| Tulare | 754 | 181 | 76 | 42% |
| Tuolumne | 92 | 8 | - | - |
| Ventura | 553 | 102 | 24 | 24% |
| Yolo | 534 | 58 | 9 | 16% |
| Yuba | 103 | 8 | - | - |
| State Totals | 34395 | 5998 | 2532 | 42% |
* Birds in a die-off are not included in reported totals because the deaths are not related to WNV. A die-off is defined as a group of 10 or more same species dead birds unless the species is American Crow.
Source: Vector-Borne Disease Section, California Department of Public Health