| County | Reported* | Tested | Positive | % Tested Positive |
| Alameda | 323 | 51 | 11 | 22% |
| Alpine | - | - | - | - |
| Amador | 10 | - | - | - |
| Butte | 185 | 43 | 22 | 51% |
| Calaveras | 25 | - | - | - |
| Colusa | 5 | 1 | - | - |
| Contra Costa | 861 | 75 | 33 | 44% |
| Del Norte | - | - | - | - |
| El Dorado | 108 | 16 | 4 | 25% |
| Fresno | 214 | 8 | 6 | 75% |
| Glenn | 15 | 6 | 4 | 67% |
| Humboldt | 19 | - | - | - |
| Imperial | 1 | - | - | - |
| Inyo | 2 | - | - | - |
| Kern | 63 | 1 | - | - |
| Kings | 22 | 6 | 4 | 67% |
| Lake | 58 | 16 | 5 | 31% |
| Lassen | - | - | - | - |
| Los Angeles | 1102 | 188 | 124 | 66% |
| Madera | 27 | 9 | 5 | 56% |
| Marin | 106 | 10 | 5 | 50% |
| Mariposa | 6 | - | - | - |
| Mendocino | 20 | - | - | - |
| Merced | 76 | 9 | 5 | 56% |
| Modoc | 6 | - | - | - |
| Mono | 2 | - | - | - |
| Monterey | 46 | 1 | - | - |
| Napa | 42 | 3 | 1 | 33% |
| Nevada | 41 | 10 | 2 | 20% |
| Orange | 682 | 407 | 91 | 22% |
| Placer | 308 | 190 | 30 | 16% |
| Plumas | - | - | - | - |
| Riverside | 157 | 41 | 16 | 39% |
| Sacramento | 1773 | 701 | 411 | 59% |
| San Benito | 5 | 1 | - | - |
| San Bernardino | 109 | 27 | 5 | 19% |
| San Diego | 737 | 367 | 264 | 72% |
| San Francisco | 52 | 8 | - | - |
| San Joaquin | 317 | 70 | 37 | 53% |
| San Luis Obispo | 31 | 5 | - | - |
| San Mateo | 529 | 111 | 15 | 14% |
| Santa Barbara | 41 | 3 | - | - |
| Santa Clara | 882 | 163 | 89 | 55% |
| Santa Cruz | 125 | 26 | 2 | 8% |
| Shasta | 53 | 4 | 3 | 75% |
| Sierra | - | - | - | - |
| Siskiyou | 5 | - | - | - |
| Solano | 144 | 30 | 13 | 43% |
| Sonoma | 175 | 24 | 8 | 33% |
| Stanislaus | 299 | 26 | 14 | 54% |
| Sutter | 79 | 24 | 10 | 42% |
| Tehama | 28 | - | - | - |
| Trinity | 1 | - | - | - |
| Tulare | 76 | 16 | 3 | 19% |
| Tuolumne | 2 | - | - | - |
| Ventura | 230 | 46 | 34 | 74% |
| Yolo | 367 | 129 | 72 | 56% |
| Yuba | 40 | 7 | 4 | 57% |
| State Totals | 10632 | 2879 | 1352 | 47% |
* 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