Researchers say a new coronavirus variant found in California may have contributed to Los Angeles' case surge

• More than 1 million people in LA county have gotten COVID-19. Two-thirds of those cases were reported in the last two months.
• According to a recent study, LA's coronavirus surge coincides with the emergence of a new variant called CAL.20C.

More than 1 million people in Los Angeles County have gotten COVID-19 since the start of the pandemic. Two-thirds of those cases were reported in the last two months.

According to a preliminary study, one factor driving the area's recent coronavirus surge may be a new variant called CAL.20C. The variant, which is different than the more infectious strains first detected in the UK (B.1.1.7) and South Africa (B.1.351), has become one of the prominent versions of the virus in LA county.

"The recent surge in COVID-19 positive cases in Southern California coincides with the emergence of CAL.20C," Dr. Eric Vail, a pathologist at Cedars-Sinai Medical Center and co-author of the new study, said in a press release.

Cedars-Sinai researchers discovered CAL.20C in a virus sample in July. As far as limited genetic testing could detect, the variant didn't appear in Southern California again until October. At the time, it didn't seem to be spreading widely in the community.

By December, however, 36% of virus samples from Cedars-Sinai COVID-19 patients were identified as CAL2.0C. The variant also represented nearly one-quarter of all samples from Southern California.

New York, Washington DC, and island countries in the Pacific Ocean have also reported cases involving the strain.

No sign CAL2.0C is deadlier

The more a virus spreads, the more it replicates, which raises the likelihood of mutations. So in places where transmission is high, we are more likely to see variants emerge.

The more infectious variants that vaccine developers and public-health experts are keeping their eyes on around the world have similar mutations in the genetic codes for their spike protein, which is what the coronavirus uses to invade cells. Tweaks in the spike protein may make it easier for variants to infect people.

CAL.20C has mutations in that part of its genetic code as well, though it lacks two key mutations that the South Africa and UK variants share. The Cedars-Sinai researchers said additional studies are needed to find out whether CAL.20C spreads more easily than other existing strains, or if it can evade the antibodies our bodies develop in response to infection with the original virus or existing vaccines.

There is no sign yet that CAL.20C is deadlier than its viral counterparts, they added.

LA hit by multiple variants

Daily COVID-19 deaths in LA tripled between early December and early January, and hospitalizations jumped from an average of about 1,000 people per day to more than 6,000. But CAL.20C isn't the only new strain circulating in LA County. Los Angeles reported its first case of the more transmissible B.1.1.7 variant first detected in the UK - which UK officials say might also be deadlier - on January 16.

Of the 293 cases involving B.1.1.7 reported in the US, 30% are in California.

When LA's case count doubled from 400,000 to 800,000 during December, mayor Eric Garcetti told the LA Times that he suspected B.1.1.7 was a factor.

"This happened devastatingly quickly. Everybody I talked to said this acceleration was beyond any model and any expectation, so then people say, 'What broke down?' and I've got to think it's partly the strain that was out there," Garcetti said.

But based on genetic data collected in the US, experts say it's unlikely the B.1.1.7 strain contributed significantly to the surge in cases so far.

"I think the evidence so far suggests that we're seeing this in really less than 1% of, of cases," Charles Chiu, an infectious-disease expert at the University of California, San Francisco, told Insider earlier this month. "But if this strain is indeed more transmissible, we may start seeing increasing proportion of infections by this strain."

The B.1.351 variant detected in South Africa hasn't been found in LA or any other part of the US yet. But Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, recently told Newsweek he wouldn't be surprised if it was already in the US.

Strains aren't responsible for all spread

Some experts caution against pitting all blame for LA county's surge on new variants.

"We cannot definitively conclude what proportion of a local outbreak is due to specific virus properties or due to human behaviors," Nathan Grubaugh, an epidemiologist at the Yale School of Medicine, told Insider. "If a variant is more transmissible, it can exacerbate an outbreak, but it's humans that will cause it."

Ultimately, all versions of the virus can be thwarted in the same way, experts say: strict mask wearing and social distancing. Grubaugh thinks the holidays and associated travel had a big impact on transmission in LA, since now "things appear to be settling down a bit in many places," he said.

Indeed, daily cases and hospitalizations in the county have been declining since the first week of January, though Southern California's ICU capacity remains at 0%. California Gov. Gavin Newsom ended stay-at-home orders and curfews across the state on Monday, citing improving case rates, positivity rates, and hospitalizations.

"Human behavior has a very large effect on transmission - probably much larger than any biological differences in SARS-CoV-2 variants," Paul Bieniasz, a virologist at the Howard Hughes Medical Institute, previously told Insider. "Americans should be doing everything they can to limit the spread of SARS-CoV-2, regardless of whether there has been a biological change in the transmissibility of circulating strains."

Aria Bendix contributed reporting to this story.