2023 SLEV Activity by County
(2025-12-03) - Source: http://westnile.ca.gov
| County | Human Cases | Mosquito Samples | Sentinel Chickens |
| State Totals | 19 | 728 | 1 |
| Alameda | - | - | - |
| Alpine | - | - | - |
| Amador | - | - | - |
| Butte | - | - | - |
| Calaveras | - | - | - |
| Colusa | - | - | - |
| Contra Costa | - | - | - |
| Del Norte | - | - | - |
| El Dorado | - | - | - |
| Fresno | 3 | 160 | - |
| Glenn | - | - | - |
| Humboldt | - | - | - |
| Imperial | - | 3 | - |
| Inyo | - | 1 | - |
| Kern | 2 | 75 | - |
| Kings | 2 | 44 | - |
| Lake | - | - | - |
| Lassen | - | - | - |
| Los Angeles | 1 | - | - |
| Madera | - | 47 | - |
| Marin | 1 | - | - |
| Mariposa | - | - | - |
| Mendocino | - | - | - |
| Merced | - | 12 | - |
| Modoc | - | - | - |
| Mono | - | - | - |
| Monterey | - | - | - |
| Napa | - | - | - |
| Nevada | - | - | - |
| Orange | - | - | - |
| Placer | - | 1 | - |
| Plumas | - | - | - |
| Riverside | 1 | 119 | - |
| Sacramento | 1 | - | - |
| San Benito | - | - | - |
| San Bernardino | - | - | - |
| San Diego | - | - | - |
| San Francisco | - | - | - |
| San Joaquin | - | 9 | - |
| San Luis Obispo | - | - | - |
| San Mateo | - | - | - |
| Santa Barbara | - | - | - |
| Santa Clara | - | - | - |
| Santa Cruz | - | - | - |
| Shasta | - | 3 | 1 |
| Sierra | - | - | - |
| Siskiyou | - | - | - |
| Solano | - | - | - |
| Sonoma | - | - | - |
| Stanislaus | 5 | 23 | - |
| Sutter | - | - | - |
| Tehama | - | - | - |
| Trinity | - | - | - |
| Tulare | 1 | 228 | - |
| Tuolumne | - | - | - |
| Ventura | - | - | - |
| Yolo | 2 | 3 | - |
| Yuba | - | - | - |
| State Totals | 19 | 728 | 1 |