| County | Reported* | Tested | Positive | % Tested Positive |
| Alameda | 1065 | 220 | 19 | 9% |
| Alpine | 6 | 2 | - | - |
| Amador | 112 | 31 | 1 | 3% |
| Butte | 1045 | 121 | 27 | 22% |
| Calaveras | 208 | 37 | 3 | 8% |
| Colusa | 50 | 12 | 4 | 33% |
| Contra Costa | 2042 | 294 | 28 | 10% |
| Del Norte | 46 | 11 | - | - |
| El Dorado | 441 | 100 | 7 | 7% |
| Fresno | 2010 | 284 | 113 | 40% |
| Glenn | 158 | 63 | 36 | 57% |
| Humboldt | 147 | 42 | 2 | 5% |
| Imperial | 11 | 2 | - | - |
| Inyo | 47 | 5 | 1 | 20% |
| Kern | 1888 | 308 | 124 | 40% |
| Kings | 191 | 34 | 9 | 26% |
| Lake | 145 | 21 | 3 | 14% |
| Lassen | 84 | 24 | 2 | 8% |
| Los Angeles | 2518 | 627 | 161 | 26% |
| Madera | 158 | 33 | 6 | 18% |
| Marin | 455 | 66 | 4 | 6% |
| Mariposa | 49 | 9 | - | - |
| Mendocino | 115 | 24 | 3 | 13% |
| Merced | 484 | 90 | 34 | 38% |
| Modoc | 19 | 7 | 1 | 14% |
| Mono | 60 | 4 | - | - |
| Monterey | 349 | 49 | - | - |
| Napa | 139 | 6 | 2 | 33% |
| Nevada | 326 | 83 | 5 | 6% |
| Orange | 833 | 191 | 32 | 17% |
| Placer | 1002 | 93 | 16 | 17% |
| Plumas | 81 | 24 | 1 | 4% |
| Riverside | 649 | 39 | 6 | 15% |
| Sacramento | 5985 | 359 | 142 | 40% |
| San Benito | 56 | 20 | - | - |
| San Bernardino | 795 | 153 | 26 | 17% |
| San Diego | 874 | 298 | 106 | 36% |
| San Francisco | 161 | 35 | 1 | 3% |
| San Joaquin | 1581 | 89 | 46 | 52% |
| San Luis Obispo | 322 | 73 | 9 | 12% |
| San Mateo | 585 | 143 | 2 | 1% |
| Santa Barbara | 208 | 25 | 1 | 4% |
| Santa Clara | 1998 | 260 | 83 | 32% |
| Santa Cruz | 357 | 82 | 6 | 7% |
| Shasta | 808 | 131 | 47 | 36% |
| Sierra | 13 | 4 | - | - |
| Siskiyou | 34 | 8 | 4 | 50% |
| Solano | 602 | 19 | 3 | 16% |
| Sonoma | 849 | 152 | 19 | 13% |
| Stanislaus | 1465 | 243 | 130 | 53% |
| Sutter | 255 | 6 | 1 | 17% |
| Tehama | 199 | 53 | 20 | 38% |
| Trinity | 60 | 13 | 1 | 8% |
| Tulare | 572 | 129 | 37 | 29% |
| Tuolumne | 146 | 32 | 1 | 3% |
| Ventura | 628 | 152 | 15 | 10% |
| Yolo | 648 | 138 | 25 | 18% |
| Yuba | 120 | 8 | 1 | 13% |
| State Totals | 36254 | 5581 | 1376 | 25% |
* 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