California’s COVID-19 positivity rate continues to soar, reaching levels rivaling the January Omicron surge that brought record cases to the state.

The California Department of Public Health on Tuesday evening reported the statewide test positivity rate at 15%, up from 13.2% the previous week. The rate is the largest the state has seen since January, and has increased tenfold since early April as new, more transmissible variants grow.

Case rates are trending upward as well, with the state reporting 39.9 new cases per 100,000 people, up 15.6% from last week. Case rates, however, are a less reliable metric, as testing volumes remain in free fall. Testing is down 45% since the beginning of June, as more residents opt to use at-home rapid tests or forego testing altogether.

Officials say that metrics beyond case rate, like wastewater, paint a more accurate picture — and they show that the current surge may rival California’s record spike in January.

Following the statewide trend, Sacramento County’s positivity rate swelled this week to 14.7%, up from 13.6% last week.

Placer, and Yolo counties also saw positivity rates grow this week — they now stand at 15.9% and 8.3%, respectively. El Dorado County bucked the trend, with its positivity rate falling to 14.5% from 14.8%.

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The state’s largest cities are also feeling the surge, with San Francisco County reporting a case rate of 51.1 — 11 higher than the state average — and a 14.9% positivity rate, up from last week. Los Angeles County saw an increase in case rate and positivity, although its 12.3% positivity rate lies well below the state average.

The increase in viral spread across the state may in part be due to the rise of more infectious omicron variants, one of which is now the dominant variant in the region and the country.

BA.5 variant dominates

The BA.5 omicron subvariant now accounts for over half the COVID-19 cases in the United States and the CDC region containing California.

BA.5, which was first identified in South Africa and Europe in February, is widely believed to be more infectious than previous omicron variants. BA.5 and its counterpart BA.4 were labeled variants of concern by the CDC when they first arrived in the United States, and various European agencies have attributed high case rates to the spread of the new variants.

This week, CDC data showed BA.5 is the dominant variant nationwide. BA.5 and BA.4 together make up over 70% of national cases.

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In the CDC reporting region that includes California and much of the West, BA.5 made up 51.9% of all new cases in the week ending July 2. BA.4 and BA.5 combine to make up 68.4%; BA.2.12.1 and BA.2, meanwhile, made up 31.5% of new cases.

Yolo County health officer Dr. Aimee Sisson said last week BA.4 and BA.5 are especially concerning to the region because they can easily reinfect people who recently had other versions of omicron, leading to high rates of spread.

Locally, BA.4 and BA.5 appear to now be dominant as well. In the final week of Healthy Davis Together — Yolo County’s testing program, which ended June 30 — BA.4 and BA.5 combined to make up just over 50% of all county tests.

Last week, Sisson said she expected viral spread and case rates “to get worse before they get better” as the new subvariants became dominant across Yolo County and the greater Sacramento region.

State announces new school guidance

California released its COVID-19 guidelines for the 2022-23 school year last week, much of which defers to local guidance for masking and distancing requirements.

The state will continue to allow school districts to set their own COVID guidelines, but urge local officials to evaluate CDC community levels and vaccination rates when creating masking and distancing plans.

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The Sacramento City Unified School District instituted a mask mandate for the final two weeks of the 2021-22 school year, after Sacramento County re-entered the CDC’s high-spread level in early June. The school district voted in March to align masking guidance with CDC community levels and will, barring any policy changes, continue the mask mandate into the fall if the county remains in the high-spread level.

The state also recommends that school districts rely on rapid antigen tests, rather than PCR tests, to track COVID-19 spread. Schools should consider testing students and staff before returning from major breaks, the guidelines say.

The state guidelines prohibit school officials from preventing students or faculty from wearing masks, and calls on local jurisdictions to come up with plans to have masks available for students who wish to wear a mask but forget to bring it to school.

Sacramento-area case rates rise, hospitalizations fluctuate

The latest surge comes with a decoupling of cases and hospitalizations, as the state’s hospitalization and death numbers have not significantly risen along with infections.

In the Sacramento region, cases and positivity have soared while hospitalizations lightly fluctuate week to week.

Sacramento County’s latest case rate — reflecting the week ending June 27 — is 37.2 per 100,000 residents, state health officials said in a Tuesday evening update. This marks a 7.8% increase from the case rate one week ago, and a 1% increase from the most recent metric released Friday.

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Hospitals in Sacramento County were treating 200 COVID-19 patients Tuesday, state data showed, up from 198 one week earlier. The intensive care unit total was 29, up four from last week.

Placer County’s latest case rate is 26.8 per 100,000 residents, a 22.4% increase from one week earlier.

Hospitals in Placer County were treating 79 virus patients Tuesday, down from 85 one week earlier. The ICU total increased to seven from six.

Yolo County’s latest case rate is 49.1 per 100,000 residents, a 20.3% increase from one week earlier. It has the sixth-largest case rate of any California county.

Hospitals in Yolo County were treating seven virus patients Tuesday, down from nine a week earlier. The ICU total held at one.

El Dorado County’s latest case rate is 30.9 per 100,000 residents, a 29.3% increase from one week earlier.

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Hospitals in El Dorado County were treating nine virus patients Tuesday, up from six a week earlier. The ICU total dropped to zero from one.

Sutter County’s latest case rate is 26.3 per 100,000 residents, down slightly from 26.5 last week. Yuba County’s is 30.1 per 100,000, up 16.2% from last week, state health officials reported Tuesday.

The single hospital serving both Yuba and Sutter counties was treating 11 virus patients Tuesday, up from 12 a week earlier. The ICU total dropped to one from two.