COVID Levels in California
In the week ending 10 October 2026, wastewater virus levels in California were High or Very High for COVID-19 at 38 of 54 sites, Flu A at 3 of 54 sites, RSV at 0 of 54 sites. COVID-19 was High or Very High at 70% of the state's sampling sites. Source: CDC wastewater surveillance.
Very High High Moderate Low Very Low
Sampling sites in California 54
| Counties served | People served | COVID-19 | Flu A | RSV |
|---|---|---|---|---|
| Los Angeles, Ventura | 4,000,000 | High | Low | Very Low |
| Los Angeles | 3,500,000 | Moderate | Very Low | Very Low |
| San Diego | 2,200,000 | High | Very Low | Very Low |
| Orange | 1,800,000 | Moderate | Moderate | Very Low |
| Santa Clara | 1,500,000 | Moderate | Low | Very Low |
| Sacramento | 1,480,000 | Very High | Moderate | Very Low |
| San Bernardino | 890,000 | Moderate | Low | Very Low |
| San Francisco, San Mateo | 750,000 | Moderate | Moderate | Very Low |
| Alameda, Contra Costa | 740,000 | High | High | Moderate |
| Fresno | 650,000 | High | Very Low | Very Low |
| Contra Costa | 487,300 | Very High | Moderate | Very Low |
| Riverside | 350,000 | Very High | Low | Very Low |
| Alameda | 342,000 | High | Moderate | Very Low |
| San Bernardino | 325,000 | High | Low | Very Low |
| Monterey | 262,000 | High | Very Low | Very Low |
| San Francisco, San Mateo | 250,000 | High | High | Low |
| Ventura | 250,000 | High | Low | Low |
| Santa Clara | 236,000 | High | Moderate | Low |
| Sonoma | 230,000 | Moderate | Low | Very Low |
| Contra Costa | 218,281 | Very Low | Very Low | Very Low |
| San Mateo | 199,000 | Moderate | Low | Very Low |
| Kern | 168,750 | Very High | Low | Low |
| Santa Cruz | 160,000 | Very High | Moderate | Very Low |
| Alameda | 160,000 | Very High | Low | Very Low |
| Santa Clara | 153,000 | Moderate | Moderate | Moderate |
| Alameda | 150,000 | High | Moderate | Very Low |
| Solano | 121,000 | Very High | Low | Very Low |
| Santa Clara | 110,338 | Very High | Low | Very Low |
| Placer | 108,444 | Very High | Low | Very Low |
| Marin | 104,250 | High | Low | Very Low |
| Butte | 101,299 | Very High | Low | Very Low |
| Alameda | 95,000 | Very High | Low | Very Low |
| Riverside | 91,765 | High | Low | Very Low |
| Merced | 91,000 | Very High | Low | Very Low |
| Stanislaus | 86,000 | High | Very Low | Very Low |
| Napa | 83,300 | Moderate | Low | Very Low |
| Santa Barbara | 77,600 | Moderate | Low | Very Low |
| Sutter | 70,000 | Very High | Very Low | Very Low |
| Santa Barbara | 69,290 | Very High | Low | Low |
| Yolo | 68,000 | Moderate | Low | Very Low |
| Shasta | 60,000 | High | High | Very Low |
| Yolo | 59,000 | Very High | Low | Very Low |
| Kings | 56,000 | Moderate | Very Low | Very Low |
| Marin | 53,000 | Very High | Moderate | Very Low |
| El Dorado, Nevada, Placer | 50,000 | Moderate | Low | Very Low |
| San Luis Obispo | 47,545 | Very High | Moderate | Low |
| Humboldt | 45,000 | High | Low | Very Low |
| Butte | 44,000 | High | Moderate | Very Low |
| San Luis Obispo | 31,037 | Moderate | Low | Very Low |
| Shasta | 29,000 | High | Moderate | Very Low |
| Napa | 20,256 | High | Moderate | Very Low |
| Del Norte | 15,372 | Moderate | Very Low | Very Low |
| Lake | 13,200 | Very High | Very Low | Very Low |
| Plumas | 4,217 | High | Very Low | Very Low |
When levels are high where you live
- Stay current on vaccines for COVID-19 and flu, and RSV if you are 75+, 50–74 with risk factors, pregnant, or have an infant.
- Test if you have symptoms; antivirals for COVID-19 and flu work best in the first days and are meant for people at higher risk.
- A well-fitting mask in crowded indoor places and better ventilation cut the risk for you and for people around you.
- Stay home when sick. Outbreak news is in our epidemic record.
What this page shows, and what it misses
CDC's weekly wastewater viral activity level for each sampling site — a treatment plant or a point upstream — compared with that site's own baseline, in five categories from Very Low to Very High. State rows count sites; CDC's own state level, on its map, weighs sites differently and can differ from what these counts suggest. Places not on a sewer system, and sites that did not report this week, are not covered. Wastewater shows community spread, not the number of cases.
Data: Centers for Disease Control and Prevention, National Wastewater Surveillance System, "CDC Wastewater Viral Activity Level for SARS-CoV-2, Influenza A and RSV" (data.cdc.gov) — public domain U.S. Government work.