SACRAMENTO, Calif. — Coronavirus infections have continued a steady climb in California since early April, and while the curve of new cases remains less steep than winter’s omicron variant surge, the rising spread of two contagious subvariants is still prompting concern about a fresh wave of virus cases.
The California Department of Public Health on Friday reported the statewide daily case rate for COVID-19 at 14 per 100,000 residents, a 27% increase in the past week and up 71% in the past two weeks.
Test positivity has spiked from 2.8% to 3.9% in the past week for California’s highest reading since Feb. 18, when the state remained on the downslope of the omicron surge.
California’s case rate dipped as low as 5.2 per 100,000, and positivity as low as 1.2%, in mid-March.
Hospitals statewide were treating 1,112 patients with confirmed COVID-19 Thursday, after bottoming out at 950 on April 25, for a 17% jump in the past 10 days. Virus patients in intensive care units during the same window spiked 50%, from 112 to 168, CDPH reported Friday.
Some of the state’s highest transmission rates are now being recorded in the San Francisco Bay Area. San Francisco now has the highest daily case rate at 32 per 100,000, a 66% increase compared to two weeks earlier.
The next four counties by case rate in Friday’s update were San Mateo at 28 per 100,000, Santa Cruz at 28 per 100,000, Santa Clara at 25 per 100,000 and Alameda at 22 per 100,000.
San Francisco also has the state’s fourth-highest positivity rate at 8.6%, behind only Imperial County at 10.3% and the state’s two least populous counties, Alpine and Sierra, both at 14.3%. Marin and Sonoma counties each recorded 7.8% positivity, double the state average.
More concerning, the number of patients hospitalized with COVID-19 in San Francisco has more than doubled in the past 10 days from 26 to 55, according to state health figures updated Friday. San Francisco’s ICU total shot from three to 10.
The U.S. Centers for Disease Control and Prevention, in an update this week to its three-tiered, nationwide map of “community levels” for COVID-19, showed Marin, San Francisco, San Mateo, Santa Clara and Santa Cruz counties in the “medium” level of coronavirus activity. California’s remaining 53 counties are in the “low” level.
Virus metrics vary across counties in the Sacramento region, currently better than most Bay Area counties but slightly worse than the state average.
High schools in both the Sacramento area and Bay Area are reporting outbreaks or clusters of COVID-19 cases, some of them coming a couple of weeks after many schools held prom or similar dance events and a few weeks after spring break.
“We are seeing an uptick in cases in general and we have seen an uptick in cases and outbreaks being reported by schools in recent weeks,” Sacramento County health office spokeswoman Samantha Mott said in an emailed statement Thursday.
A pair of highly transmissible omicron subvariants, known as BA.2 and BA.2.12.1, now make up a vast majority of U.S. cases, with the prevalence of the latter creeping upward. The two variants are likely responsible in large part for California’s rising transmission rates.
BA.2.12.1, the more contagious of the two, made up an estimated 37% of cases nationwide for the week of April 24 to April 30, according to a weekly update Tuesday from the CDC, up from 27% the prior week. BA.2 decreased from 70% to 62%, suggesting BA.2.12.1 may soon overtake it.
For the CDC region that includes California, Arizona, Nevada, Hawaii and Pacific territories, BA.2.12.1 increased from 12% to 18% in the past week, while BA.2 dropped from 85% to 81%.
Health officials have estimated BA.2 is about 40% more transmissible than the original omicron variant, BA.1; and BA.2.12.1 is believed to be about 25% more contagious than BA.2.
Yolo County health officials last week, in a joint news release with the Healthy Davis Together testing initiative, said BA.2.12.1 “now accounts for nearly half of campus cases” at the University of California, Davis after being first detected there in late March.
“Data show that COVID-19 is spreading in Yolo County, especially in Davis. Yolo residents are encouraged to take additional precautions to guard against infection,” Yolo County health officer Dr. Aimee Sisson said in a prepared statement.
“I strongly recommend masking indoors with a high-quality mask and getting tested if you have symptoms, have a known exposure, or recently participated in a large gathering like Picnic Day,” which was held April 23, Sisson said. “If you are eligible for a booster, now is a good time to get that booster — do not wait.”
It is still not fully clear how much immune protection Californians may maintain from the immense wave of infections during the omicron surge, which pushed the case rate above 300 per 100,000 and positivity above 22% in early January, as experts study the new subvariants’ ability to evade prior immunity.
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