| County | Reported* | Tested | Positive | % Tested Positive |
| Alameda | 509 | 82 | 19 | 23% |
| Alpine | - | - | - | - |
| Amador | 14 | - | - | - |
| Butte | 322 | 82 | 38 | 46% |
| Calaveras | 18 | - | - | - |
| Colusa | 16 | 4 | 3 | 75% |
| Contra Costa | 915 | 49 | 11 | 22% |
| Del Norte | 3 | 1 | - | - |
| El Dorado | 136 | 26 | 4 | 15% |
| Fresno | 187 | 10 | 3 | 30% |
| Glenn | 16 | 5 | 4 | 80% |
| Humboldt | 33 | 9 | 2 | 22% |
| Imperial | 3 | - | - | - |
| Inyo | 3 | - | - | - |
| Kern | 58 | 1 | 1 | 100% |
| Kings | 22 | 7 | 3 | 43% |
| Lake | 60 | 21 | 5 | 24% |
| Lassen | 6 | - | - | - |
| Los Angeles | 1209 | 164 | 103 | 63% |
| Madera | 16 | 3 | 1 | 33% |
| Marin | 172 | 14 | 3 | 21% |
| Mariposa | 9 | - | - | - |
| Mendocino | 20 | - | - | - |
| Merced | 114 | 13 | 3 | 23% |
| Modoc | 7 | - | - | - |
| Mono | 9 | - | - | - |
| Monterey | 37 | 5 | - | - |
| Napa | 77 | 11 | 7 | 64% |
| Nevada | 55 | 17 | 10 | 59% |
| Orange | 674 | 427 | 83 | 19% |
| Placer | 361 | 192 | 21 | 11% |
| Plumas | 4 | - | - | - |
| Riverside | 358 | 110 | 82 | 75% |
| Sacramento | 1063 | 363 | 103 | 28% |
| San Benito | 16 | 2 | - | - |
| San Bernardino | 281 | 41 | 25 | 61% |
| San Diego | 980 | 550 | 355 | 65% |
| San Francisco | 109 | 15 | - | - |
| San Joaquin | 301 | 68 | 18 | 26% |
| San Luis Obispo | 41 | 1 | - | - |
| San Mateo | 687 | 158 | 23 | 15% |
| Santa Barbara | 71 | 8 | 3 | 38% |
| Santa Clara | 1575 | 357 | 231 | 65% |
| Santa Cruz | 140 | 43 | - | - |
| Shasta | 132 | 26 | 16 | 62% |
| Sierra | - | - | - | - |
| Siskiyou | 5 | - | - | - |
| Solano | 177 | 14 | 10 | 71% |
| Sonoma | 283 | 36 | 11 | 31% |
| Stanislaus | 323 | 44 | 14 | 32% |
| Sutter | 102 | 43 | 16 | 37% |
| Tehama | 27 | - | - | - |
| Trinity | 11 | 6 | 2 | 33% |
| Tulare | 137 | 44 | 23 | 52% |
| Tuolumne | 11 | 2 | - | - |
| Ventura | 254 | 36 | 26 | 72% |
| Yolo | 313 | 124 | 61 | 49% |
| Yuba | 54 | 16 | 6 | 38% |
| State Totals | 12536 | 3250 | 1349 | 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