The Omicron strain of the coronavirus was detected in California’s wastewater last month, even before the World Health Organization declared it a “variant of concern,” lab data suggests.

In a statement to The Times, the California Department of Public Health said that a sample of wastewater collected in Merced County on Nov. 25 contained a mutation that suggests the Omicron variant was present in California at that time.

That’s one day after South African scientists informed the World Health Organization of the new variant and a day before the WHO gave it the name Omicron and declared it the newest coronavirus variant of concern.

The finding reinforces observations that scientists have made in recent weeks: that Omicron was rapidly spreading across the world before global health officials were aware it existed.

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