Two recent studies based on COVID testing in San Francisco's Mission District offer some insight into the so-called California variant of the coronavirus, which appears to be becoming more prevalent locally with each week. Scientists say that people infected with the variant appear to have both a higher chance of spreading it, and a higher probability of ending up hospitalized or dead from COVID-19.

The bad news comes from studies out of UCSF and the Chan Zuckerberg Biohub, as the Chronicle reports, and the only slightly good news is that while this newer variant appears to be more transmissible than original versions of the virus, it is not quite as highly transmissible as the UK variant. The studies found that when one case of the new variant entered a home in the Mission District, 35% of household members became infected, compared to about 26% who were normally infected by earlier strains when they were introduced.

The UK variant was found to be between 50% and 70% more transmissible than original strains.

Like other variants circulating in the world, the California variant has a key mutation in its "spike" protein that makes it more easy to attach to human cells.

"We don’t want to be alarmist," says Joe DeRisi, co-president of the Biohub. "It’s not as aggressive as the U.K. variant... [But] we need to be aware that it’s in the community and spreading fast."

And Dr. Charles Chiu at UCSF writes that the California variant "should likely be designated a variant of concern warranting urgent follow-up investigation."

While approximately 16% of positive tests in the Mission District were appearing with this new variant back in November, that has risen to more than 50% as of January, according to the researchers.

Like the UK variant did not long after it appeared, this California variant seems likely to become the dominant strain wherever it takes hold.

"The Latinx community continues to be disproportionately impacted by COVID-19 and the uptick of the L452R variant among our community is concerning,” said Jon Jacobo, health committee chair with the Latino Task Force — which collaborated with researchers in a volunteer-based coalition called Unidos en Salud. “Unidos en Salud is an important partnership to help track and contain the virus. It’s a model that I believe should be adapted in communities across the country.”

It's not clear how widespread the variant has become in the region, and it is spreading at a time when test-positivity rates and overall case numbers are falling steadily in every Bay Area county. Still, all nine counties are still in the "Purple" tier as of Monday, and experts worry that more aggressive strains could lead to another surge in cases before the vaccine rollout covers enough of the population.

The Mercury News reports, via the studies, that researchers assume from their testing that the variant now represents about half of all cases in California. First detected in Denmark last March and in Los Angeles last May, the variant is sometimes referred to by a single mutation as L452R, but also referred to as CAL20.C, and the CA Department of Public Health says it is actually two separate but similar variants known as B.1.429 and B.1.427.

Because it appears less transmissible than the UK variant (known as B.1.117), and less resistant to existing vaccines than the South African and Brazilian variants, the Mercury News suggests we can see the California variant as "less ominous" than these others. There was, however, a two- to four-fold reduction seen in lab tests in the ability of antibodies to fend off the California variant, so it's still kind of ominous.

UCSF infectious disease expert Dr. Monica Gandhi sounded a note of optimism, however, speaking to KPIX over the weekend. "I’m hoping after this [last surge], that we can use our principles – masking, ventilation, and distancing — and we will be able to stay open in this same way and even get better, and with vaccines coming on board, I’m hoping we’ll never have another surge again."

Reminder: wear two masks! Don't get complacent!