Walnut Creek residents heading into fall should take extra precautions against COVID-19, Contra Costa Health warned Monday, Aug. 24, saying the virus is on the rise across the county.
The agency did not release specific case counts or hospitalization data. National indicators also show COVID activity increasing. WastewaterSCAN reported rising concentrations nationally, particularly in the West and South, while national reporting has identified California among states experiencing a sharp uptick.
Contra Costa Health posted the advisory in both English and Spanish on its official X account on Monday, Aug. 24, linking residents to the agency's COVID-19 information page at cchealth.org.
Claycord reported on the county warning Tuesday, Aug. 25.
No local data was released.
What the county recommends
The health department listed five steps residents should take:
- Stay up to date on COVID vaccinations
- Test when needed
- Consider wearing masks in crowded indoor spaces
- Wash hands frequently
- Stay home when feeling sick
County health officials said residents should consider these precautions as COVID activity increases and flu and RSV season approaches.
National context
The advisory lands during what infectious disease experts are calling a predictable late-summer COVID wave. WastewaterSCAN, a Stanford University-led tracking tool, reported that national COVID levels in August were up 105% compared to July, with concentrations doubling each month since June. In the West and South, wastewater readings have already surpassed levels seen during the previous winter peak.
Amanda Bidwell, scientific program manager for WastewaterSCAN and a Bay Area resident, told CNN on Aug. 20 that she personally checks local wastewater data before deciding whether to mask at concerts or airports.
"We're still seeing lower SARS-CoV-2 concentrations than at this time last year, but sites are trending upward across the country," Bidwell told USA Today on Aug. 22.
The current wave appears less severe than last summer's surge. During the week ending Aug. 13, nearly 5% of COVID tests came back positive, compared to over 9% at the same point in 2025, according to NBC News. Emergency department visits remain very low nationally.
Vaccines and treatment
About 17.5% of U.S. adults received the previous COVID vaccine, according to national reporting.
Adults over 65, infants, immunocompromised individuals and people who have never been vaccinated face the highest risk of severe illness. Paxlovid remains available as an antiviral treatment, though it is no longer free. The FDA also approved Xocova in 2026 for post-exposure prevention of COVID-19 in people 12 and older. The prescription antiviral is intended to begin within 72 hours after contact with someone who has COVID-19.
Updated 2026-27 COVID vaccines were not yet available as of Aug. 25, with national health reporting indicating they are expected sometime in September. Contra Costa Health has not announced a local availability date in connection with this advisory.
