15 cases of ‘stealth omicron’ found in Sonoma County; real number likely higher

Sonoma County health officials have detected at least 15 local cases of the highly contagious coronavirus subvariant BA.2, the increasingly dominant strain worldwide, and the same one causing a troubling surge of cases in the United Kingdom.

BA.2, which is believed to be more infectious than the original omicron strain, has not been shown to cause more severe illness. Last week, CDC chief Dr. Rochelle Walensky said the variant was now behind 35% of cases across the nation and half of cases in parts of the northeast United States.

Though only 15 cases of BA.2 have been detected locally, there are likely more since not all local infections are currently genotyped, said Kathryn Pack, health program manager of the county’s epidemiology team. Pack said local infection samples are genotyped at the county’s public health lab (up to 64 a week, while others are processed by state labs and federal labs.

She said certain infections are prioritized for genotyping to increase the likelihood of detecting concerning new variants. These include cases related to international travel; hospitalizations involving severe illness and death; large outbreaks; and booster breakthrough cases.

“Another caveat is that there is a delay between case identification and genotyping result of at least 2 weeks, but often longer,” Pack said in an email.

Pack said state modeling for BA.2 shows that it’s likely predominant in California as of last week. She said locations in Southeast and East Asia currently experiencing the largest surges have had very few previous cases, and therefore have fundamentally different immune histories than California.

Dr. Sundari Mase, Sonoma County’s health officer, advised continued vigilance against the virus given all the uncertainty about future variants and the impact of BA.2. She said there continues to be a strong recommendation for indoor masking, though it is no longer mandated.

Mase said she fully expects cases in Sonoma County to increase because of BA.2, but that increase may not see as big a surge as some had predicted. She said her “main concern” was the appearance of other, more dangerous variants, though those are not likely to appear in Sonoma County but rather in parts of the world where vaccination rates are much lower.

“That’s where variants are started — delta started in India and then omicron started in South Africa,” she said.

Currently, 81% of Sonoma County residents 5 and older have been fully vaccinated.

As of Friday, there were an average of 6 new daily infections per 100,000 residents in Sonoma County. That’s about 30 new COVID-19 cases a day, a far cry from the more than 1,000 new cases that were popping up daily mid-January, when the omicron variant was dominant.

Pack said the current effective reproductive number, “r-effective,“ of COVID-19 in Sonoma County is 0.78, which suggests that transmission is decreasing. But she pointed out that San Francisco’s r-effective rate just surpassed 1. Anything over 1 means the virus is likely spreading.

Pack said the greatest proportion of local infections is occurring among residents 10 to 39. Sonoma County case rates remain low across race and ethnic categories, with the highest rates currently found among black residents, at 8.86 infections per 100,000 residents..

In contrast, the infection rate for Latinos is 4.55 new cases per 100,000 people, while the rate for whites and Asians is 6.22 and 6.3 new cases per 100,000 residents, respectively.

Last week, county officials reported the latest COVID-19 deaths, bringing the pandemic total to 487. The deaths included a fully vaccinated and boosted man between 50 and 60 who died Jan. 26. The case was investigated by the coroner’s office, which resulted in a delay in reporting, officials said.

The other two deaths included an unvaccinated woman between 60 and 70 who died March 14 and a fully vaccinated and boosted man between 60 and 70 who died March 15. All three residents had underlying health problems, officials said.

The number of COVID-19 hospitalizations in Sonoma County have greatly decreased since the winter surge. As of Thursday, the latest data available, 11 people hospitalized in Sonoma County had tested positive for the virus, three of them were being treated in intensive care.

A spokesman at Santa Rosa Memorial Hospital said Friday the facility was seeing a “five-fold reduction in COVID-19 volumes over the course of the last two months.” There have also been some days where there have been no COVID-19 patients in ICU.

But Memorial Hospital officials said COVID-19 is still circulating in the local community and the hospital continues to treat patients with COVID-19 and other conditions.

You can reach Staff Writer Martin Espinoza at 707-521-5213 or martin.espinoza@pressdemocrat.com. On Twitter @pressreno.