Coronavirus infections in King County have skyrocketed in the past week as the omicron variant continues to surge, flying past the county’s previous highest case number, according to county data updated Monday.

The county has seen a 195% increase in cases in the past seven days, averaging 1,586 infections per day, according to the county’s COVID-19 data dashboard. It’s unclear how many of those cases are attributed to omicron, but local health experts have been predicting a “rapid surge” from the variant that could overwhelm the region’s health care systems and disrupt businesses and schools as employees get sick.

The recent spike marks the highest number of daily cases in King County since the beginning of the pandemic. The county recorded 2,267 confirmed and probable coronavirus cases last Thursday, about three-and-a-half times the peak during the delta wave, which hit a seven-day average of about 630 cases in late August..

Meanwhile, incomplete data from the state Department of Health showed 6,235 new cases statewide on Friday, which would be another record.

In a statement Monday, Public Health – Seattle & King County added that the figures are likely an underestimate because there have been delays in reporting, and rapid, over-the-counter tests were not included in the data.

“I know this news of a new surge of cases is coming after two long and exhausting years of our community working so hard to protect one another,” Dennis Worsham, interim director of King County’s health department, said in a statement. “… If you are vaccinated and boosted, you are doing your part both to protect yourself and all those around you.”

Advertising

On Christmas Eve, 13% of UW Medicine’s collected samples in Seattle returned positive for the coronavirus, the highest positivity rate the sites have ever seen, said Dr. Patrick Mathias, vice chair of clinical operations for the UW’s Department of Laboratory Medicine and Pathology, on Monday.

More on the COVID-19 pandemic

The highly transmissible omicron variant surpassed delta and became the dominant coronavirus variant in King County last week. Dr. John Lynch, Harborview Medical Center’s medical director for infection prevention and control, said omicron will likely outpace delta statewide in a “matter of days to weeks.”

Recent spread has generally hit South King County cities harder than Seattle, Shoreline, Kirkland, Redmond, Bellevue and other Eastside cities. Auburn, Kent and Federal Way, for example, have an infection rate of about 14,000 cases per 100,000 residents — compared to about 6,700 cases per 100,000 in Seattle.

In addition, while more fully vaccinated people are testing positive for the virus, county data shows unvaccinated people still pose a higher risk of transmission. As of mid-December, fully vaccinated people were becoming infected with the coronavirus at a rate of about 15.3 cases per 100,000 people — more than triple the rate of late November — while unvaccinated people were getting sick at a rate of about 81.6 cases per 100,000, according to the county dashboard.

While the vast majority of recent cases have not resulted in hospitalization, the county’s COVID hospitalizations are also again on the rise. Last week, Public Health – Seattle & King County reported a 2% increase in hospitalizations over the week before. On Monday, the county confirmed a 58% increase in the past week, with nearly 80 hospitalizations since Thursday.

Advertising

This month’s rise in infections and hospitalizations hasn’t yet translated into higher death rates, the county reported, though in the past there’s been about a monthlong gap between a change in case rates and death rates.

Statewide COVID data hasn’t been updated since last week because of the Dec. 24 holiday, but it last showed the seven-day average infection rate increased slightly between Dec. 4 and Dec. 13, from 112.5 cases per 100,000 people to 116.8 cases per 100,000, according to data from the state Department of Health.

Seattle scientists and virologists have been predicting a significant omicron surge for the past few weeks and continue to urge people to get vaccinated and boosted.

Early reports show the illness caused by omicron might be milder than that caused by the delta variant, though experts remained largely unsure of the variant’s severity. In addition, county health officer Dr. Jeff Duchin said last week that omicron’s high rate of transmissibility could soon be a problem for the region’s already strained hospitals.

Nationwide, omicron has become the dominant strain and is causing nearly vertical case growth in several U.S. cities, with figures doubling every two to three days, The New York Times reported last week.

The Centers for Disease Control and Prevention on Monday updated its guidance for isolating and quarantining, saying it’s shortening the recommended time for isolation from 10 days to five days if asymptomatic, followed by five days of mask-wearing around others.

Advertising

The change, the CDC said, is “motivated by science demonstrating that the majority of SARS-CoV-2 transmission occurs early in the course of illness.”

For people who have been exposed to the coronavirus but have not received a booster shot, the CDC is also recommending quarantining for five days followed by “strict” mask use for another five days. Those who have been boosted do not need to quarantine following an exposure, but should wear a mask for 10 days after being exposed, the CDC said.

The CDC noted that early data from South Africa and the U.K. shows two doses of an mRNA vaccine are about 35% effective at preventing infection, while an additional booster ups efficacy to about 75%.

New York, which has reported record numbers recently and reinstated mask mandates earlier this month, confirmed a high of 49,708 new cases on Christmas Eve.

The nation’s high for average daily cases was set in January at 251,232 infections. In comparison, some estimates predict the country could reach 1 million cases per day this winter.

The alarming surge has prompted Dr. Anthony Fauci, President Joe Biden’s medical adviser, to suggest a domestic travel vaccination mandate should be considered, and that people should try to avoid large New Year’s Eve parties this week.

Navigating the pandemic

More