Update: 30 COVID-19 cases tied to Davis holiday party in Yolo omicron outbreak
Yolo County, which detected the Sacramento region’s first confirmed case of the COVID-19 omicron variant less than two weeks ago and late last week identified an outbreak of six cases linked to a high school classroom, has discovered 42 additional cases of the highly contagious variant, many of them linked to a different outbreak.
The Healthy Davis Together initiative, which tests most positive samples across Yolo County for variants, in a news release Wednesday said it discovered those cases across Davis, El Macero, West Sacramento and Woodland between Dec. 12 and Saturday. The prior seven cases had only been found in West Sacramento.
An outbreak of at least 16 cases has been linked to “a single workplace holiday party” in Davis, Healthy Davis Together and Yolo County public health officials announced in a joint statement.
About 50 people attended the party, officials wrote, and 16 employees contracted the virus either at the party or from “subsequent workplace spread.” Ten of the cases have been confirmed as omicron.
Of the 16 cases, all were fully vaccinated and eight had received a booster dose.
Yolo spokesman John Fout in an emailed response to The Sacramento Bee said all 16 cases had mild or no symptoms. The county’s statement also said all known cases “are in isolation or have completed isolation.”
In an update Thursday, Fout said 30 COVID-19 cases are now linked to the holiday party in Davis, which includes people who attended the party or others who were a close contact of an attendee.
The county spokesman said the party was held indoors at an “off-site location,” and masks were not worn by attendees while eating and drinking at the party. Fout said the ages of the people who tested positive for the virus in the Davis outbreak ranged from 20s to 40s.
Subsequent workplace exposures likely occurred several days later during a gathering in a workplace breakroom in which attendees were not wearing masks while eating and drinking, Fout said.
The county news release said omicron last week made up 41% of cases tested for variants, while the Healthy Davis Together website as of Thursday morning said it comprised 43%, skyrocketing from less than 3% the prior week. About 55% of last week’s sampled cases were the delta variant, while the remaining 2% were “miscellaneous” variants.
Gov. Gavin Newsom during a Wednesday news conference said the state’s health department estimates omicron as making up more than 50% of recent case samples. Newsom called that a conservative estimate, and he said the precise figure will be provided in a weekly update Thursday.
“The spread of Omicron is coming at a time when many people are traveling and gathering for the holidays,” Yolo County public health officer Dr. Aimee Sisson said in a prepared statement. “Everyone, including fully vaccinated persons, should take additional precautions right now.”
“Wear a mask that fits and filters well when you are indoors, improve indoor ventilation with portable air filters, and ask everyone attending a gathering to test right before the event. In addition, anyone who isn’t vaccinated or boosted should get vaccinated as soon as possible in order to protect themselves against severe COVID-19 illness.”
On Thursday Sisson said in an email to The Bee that vaccines still protect against severe illness and death, but additional protections are needed for safe gatherings. The county public health officer said indoor environments are higher risk than outdoors, and removing masks to eat and drink creates opportunities for exposures.
If eating and drinking will occur indoors, hosts should require guests to provide proof of a recent negative test and take steps to improve ventilation of the indoor space, such as adding a portable HEPA filter.
Sacramento County on Tuesday confirmed its first two cases of the omicron variant, in two people with no link to each other and no history of recent travel.
Yolo County has the region’s most robust surveillance for genetic variance due to a partnership with the UC Davis Genome Center.
Omicron is rapidly overtaking delta as the dominant variant of the coronavirus, reported earlier this week by the Centers for Disease Control and Prevention as making up 73% of sampled specimens. Researchers are still determining how its severity compares to delta, which had been dominant in Yolo County and across California since July.
Experts are expressing increased levels of concern as omicron appears to be responsible for outbreaks among groups of fully vaccinated people.
Health officials in Alameda County on Dec. 3 identified an outbreak of a dozen confirmed or likely omicron cases, tied to a Nov. 27 wedding in Wisconsin attended by one of the Bay Area residents. All 12 cases were fully vaccinated, and “most” of them had received booster doses, Alameda health officials said earlier this month.
UC Davis on Tuesday announced it will begin the winter 2022 quarter with instruction on a remote-only basis the first week, Jan. 3 to Jan. 7, due to omicron concerns. The remaining six University of California undergraduate campuses on the quarter system, in separate statements Tuesday, announced a two-week transition to virtual learning.
Both the UC and California State University systems said this week that they will require booster doses for students, faculty and staff.
This story was originally published December 22, 2021 at 1:15 PM.
