| County | Reported* | Tested | Positive | % Tested Positive |
| Alameda | 911 | 166 | 96 | 58% |
| Alpine | 1 | - | - | - |
| Amador | 19 | - | - | - |
| Butte | 181 | 45 | 22 | 49% |
| Calaveras | 16 | - | - | - |
| Colusa | 15 | 6 | 4 | 67% |
| Contra Costa | 1355 | 114 | 44 | 39% |
| Del Norte | 1 | 1 | - | - |
| El Dorado | 129 | 36 | 7 | 19% |
| Fresno | 302 | 12 | 9 | 75% |
| Glenn | 10 | 8 | 4 | 50% |
| Humboldt | 21 | 4 | 2 | 50% |
| Imperial | 1 | - | - | - |
| Inyo | 2 | - | - | - |
| Kern | 82 | 4 | 3 | 75% |
| Kings | 29 | 3 | 3 | 100% |
| Lake | 102 | 43 | 18 | 42% |
| Lassen | - | - | - | - |
| Los Angeles | 1642 | 155 | 99 | 64% |
| Madera | 36 | 10 | 5 | 50% |
| Marin | 150 | 16 | 6 | 38% |
| Mariposa | 3 | - | - | - |
| Mendocino | 30 | - | - | - |
| Merced | 128 | 12 | 8 | 67% |
| Modoc | 1 | - | - | - |
| Mono | 3 | - | - | - |
| Monterey | 50 | 6 | - | - |
| Napa | 117 | 13 | 12 | 92% |
| Nevada | 47 | 11 | - | - |
| Orange | 1262 | 685 | 431 | 63% |
| Placer | 373 | 162 | 40 | 25% |
| Plumas | 4 | - | - | - |
| Riverside | 141 | 15 | 1 | 7% |
| Sacramento | 1735 | 535 | 294 | 55% |
| San Benito | 18 | 1 | - | - |
| San Bernardino | 238 | 36 | 17 | 47% |
| San Diego | 310 | 150 | 39 | 26% |
| San Francisco | 92 | 4 | - | - |
| San Joaquin | 377 | 94 | 53 | 56% |
| San Luis Obispo | 32 | - | - | - |
| San Mateo | 502 | 147 | 21 | 14% |
| Santa Barbara | 34 | 7 | 2 | 29% |
| Santa Clara | 3950 | 1097 | 925 | 84% |
| Santa Cruz | 153 | 34 | 1 | 3% |
| Shasta | 84 | 10 | 6 | 60% |
| Sierra | - | - | - | - |
| Siskiyou | 6 | - | - | - |
| Solano | 357 | 48 | 33 | 69% |
| Sonoma | 559 | 59 | 37 | 63% |
| Stanislaus | 445 | 71 | 47 | 66% |
| Sutter | 104 | 43 | 19 | 44% |
| Tehama | 19 | - | - | - |
| Trinity | 4 | - | - | - |
| Tulare | 156 | 58 | 40 | 69% |
| Tuolumne | 8 | - | - | - |
| Ventura | 144 | 38 | 7 | 18% |
| Yolo | 379 | 116 | 71 | 61% |
| Yuba | 66 | 30 | 16 | 53% |
| State Totals | 16936 | 4105 | 2442 | 59% |
* 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