Scientists in La Jolla hustle to find out whether ‘California’ strain of coronavirus poses a big threat

An electron microscope image shows SARS-CoV-2, the coronavirus that causes COVID-19.
(National Institute of Allergy and Infectious Diseases)

The new variant has been showing up throughout the state, including San Diego County.


Scientists at two institutions in La Jolla are hustling to help find out whether a new strain of the coronavirus that’s spreading in California is more infectious than the original virus and likely to cause more sickness and fatalities.

The strain, tentatively named the California variant, or CAL.20C, was discovered last summer. But scientists say it didn’t begin to spread widely across the state until late last year and that it recently began showing up in San Diego County, where various strains of the virus have killed more than 2,100 people.

UC San Diego and Scripps Research in La Jolla jointly found the new mutant in 12 out of 186 virus samples sequenced in recent days. And UC San Francisco says in a new study that it found CAL.20C in approximately 20 percent to 30 percent of the samples it sequenced recently.

“New variants pop up all of the time,” said Dr. Davey Smith, director of infectious diseases at UC San Diego. “We only become concerned when one appears to be more transmissible than others. And we suspect that this one might be more infectious than other versions.”

Smith is working with Scripps Research immunologist Kristian Andersen, who said, “We currently don’t know if it’s more transmissible and will need much more data to assess that.”

“It’s worth emphasizing that we can’t blame current surges on functional changes in the variants, as the vast majority of the spread is due to our continued failure to mobilize sufficient countermeasures such as appropriate social distancing, universal face mask usage, much more large-scale testing and screening, and avoidance of crowded settings,” Andersen said.

Scientists are trying to determine whether the variant actually evolved in California. Officials at Cedars-Sinai Medical Center in Los Angeles say the mutant did arise in California. But Smith said Jan. 20 that “that hasn’t been determined yet. It could have happened someplace else.”

UCSD and Scripps Research are now helping with a larger effort by scientists to determine how infectious CAL.20C is and whether it can be neutralized by the COVID-19 vaccines now in use.

It already appears that CAL.20C recently contributed to several outbreaks in Santa Clara County, according to public health officials.

“In addition to Santa Clara County, the variant has been detected in Humboldt, Lake, Los Angeles, Mono, Monterey, Orange, Riverside, San Francisco, San Bernardino, San Diego and San Luis Obispo counties,” Santa Clara health officials said in a statement. Researchers are certain that CAL.20C has spread to other states as well, having confirmed its presence in Arizona, Connecticut, Maryland, New Mexico, Nevada, New York, Texas, Utah, Washington and Wyoming, as well as the District of Columbia.

A highly infectious version of the coronavirus that took root in England last year spread to the United States and contributed to the big surge in infections that occurred nationwide over the holidays, according to public health officials.

— The New York Times contributed to this report.