Signs of Omicron found in California wastewater, suggesting variant is widespread

Signs of the Omicron variant of the coronavirus have been found in California’s wastewater, officials said, as the number of cases associated with the new variant rose to double digits this week, including a newly confirmed infection in a Long Beach resident.

Clues suggestive of Omicron’s presence in the Central Valley were picked up in wastewater samples collected in Sacramento and Merced counties, California state epidemiologist Dr. Erica Pan said Tuesday in a discussion hosted by the California Medical Association.

“We definitely are seeing Omicron across the state, for sure,” Pan said.

In Sacramento County, Stanford University researchers detected a distinctive mutation that is found in Omicron from wastewater collected Nov. 30, according to a statement provided by county spokesperson Janna Haynes. Results were confirmed Monday, the county said.

“These findings indicate that the Omicron variant is most likely present in Sacramento County,” the statement said.

Pan said the mutation was also found in a wastewater sample collected in Merced County.

Of the 10 people confirmed to have Omicron in California, five reside in Alameda County, four in Los Angeles County and one in San Francisco.

Long Beach reported the latest case of the Omicron variant Tuesday, in a fully vaccinated resident who was experiencing no symptoms and who had traveled abroad, although not to southern Africa. The biggest proportion of Omicron cases that have been identified have been among people in southern Africa.

The five Omicron cases in Alameda County were linked to seven other people who were also infected with the coronavirus and were guests at a wedding in Wisconsin on Nov. 27. All were under the age of 50 and had mild symptoms. And they were all vaccinated, and most had received their booster shots, Pan said.

The index case is believed to be a wedding guest who returned from Nigeria on Nov. 24 — one day before scientists in South Africa disclosed their discovery of the new variant and three days before the World Health Organization declared Omicron a variant of concern. The wedding in Wisconsin had more than 100 people, and there were events where people were masked and unmasked.

There are reasons to be concerned about how transmissible the Omicron variant is. Pan referred to a report published by the U.S. Centers for Disease Control and Prevention that detailed a case of probable airborne transmission in a Hong Kong quarantine hotel between airline passengers staying across the hallway from each other.

“Retrospective investigation, including closed-circuit television camera footage, confirmed that neither case-patient left their room during the quarantine period. No items were shared between rooms, and other persons did not enter either room,” the report said.

“The only time the two quarantined persons opened their respective doors was to collect of food that was placed immediately outside each room door. The only other time they might have opened their doors would be for [coronavirus testing], which were conducted in three-day intervals. However, because these two case-patients arrived one day apart, it is unlikely that they would be tested on the same day.”

This story originally appeared in Los Angeles Times.