Two Sacramento-area counties return to high COVID transmission, CDC says. What it means
Sacramento and Yolo counties recently returned to high community transmission rates for COVID-19, as defined by the Centers for Disease Control and Prevention, leading local health officials to reiterate calls for residents to mask up indoors and stay “up-to-date” on vaccines and boosters.
Both counties – along with Los Angeles, San Diego and several others across California including the entire Bay Area – were in the “high” transmission level as of the CDC’s latest data update Tuesday. The classification now includes just over 40% of all counties nationwide.
Counties are considered in high transmission when they have recorded more than 100 cases per 100,000 residents over the past week. The CDC recorded Yolo at 141 per 100,000 and Sacramento at 104 per 100,000 for the week preceding Tuesday’s update.
“We are now in high community transmission, with case rate continuing to increase and wastewater signals also increasing,” health officer Dr. Aimee Sisson said in a statement posted on social media Wednesday by Yolo County.
“I strongly recommend masking indoors and staying up-to-date with vaccination.”
Nearby El Dorado and Placer counties remained in “substantial” transmission as of Tuesday’s update, each near 80 weekly cases per 100,000.
California’s daily case rate has increased from about five per 100,000, in mid-March, to 16 per 100,000 as of a Tuesday data update from the California Department of Public Health.
Statewide test positivity has risen from 1.2% to 4.1%.
Schools, including in Sacramento County, are seeing a resurgence of outbreaks and case clusters for the first time since returning from winter recess during the omicron surge.
Health officials say increased virus activity is due in large part to two contagious subvariants of omicron, known as BA.2 and BA.2.12.1, gaining prevalence across the U.S.
COVID-19 surging at UC Davis
BA.2.12.1, the more contagious of the two new subvariants, made up 35% of cases at the UC Davis campus (63 of 181) and 35% of cases sequenced by the Healthy Yolo Together testing program (50 of 142) for the week of May 1 to May 7, Sisson said in an emailed response to The Sacramento Bee.
By comparison, BA.2.12.1 made up an estimated 24% of positive samples that same week for the CDC region that includes California.
BA.2.12.1 is believed to be about 25% more contagious than BA.2, which is in turn about 30% to 40% more contagious than the original omicron variant, BA.1. That makes BA.2.12.1 the most transmissible strain that has spread to date in the U.S.
BA.2 made up 62% of last week’s cases at the university, with BA.1 accounting for the remaining 3%, Sisson said. BA.2 represented 63% of Healthy Yolo Together cases, while BA.1 made up less than 2%.
UC Davis this week reported its asymptomatic test positivity rate at just over 1.5%, more than a sevenfold increase from 0.2% on April 1.
Wastewater surveillance data from the Stanford-based Sewage Coronavirus Alert Network shows that virus levels detected in Davis have roughly quadrupled since early April, now roughly halfway to peak levels from the omicron surge.
Sacramento’s wastewater virus level has roughly tripled in the past month, but as of Wednesday remained well below its omicron peak.
Sisson and the Healthy Davis Together initiative in a joint news release late last month urged students and local residents to get tested after attending a large event, such as the university’s annual Picnic Day held April 23.
What are CDC’s transmission levels?
The CDC’s four-tiered community transmission levels are distinct from its “community level” framework – which classifies counties into low, medium and high community levels based on a combination of case and hospitalization numbers. The CDC says people should wear masks indoors in counties that enter the high community level.
No local counties plan to return to mandatory masking or other health restrictions at this time. Sacramento and Yolo counties ended their local mask orders in mid-February to align with state health guidance.
Sacramento has been in the CDC’s high transmission level since April 23, as local case rates have steadily climbed. The county had been two levels lower, in “moderate” transmission, as recently as April 13. Yolo County returned to high transmission May 4.
This story was originally published May 11, 2022 at 2:22 PM.
