What we know about the ′California coronavirus′ | Science| In-depth reporting on science and technology | DW | 25.02.2021
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What we know about the 'California coronavirus'

A new strain of the coronavirus, first detected in California, may be the most virulent and deadly form of COVID-19 yet. And it's spreading internationally.

A jogger at Golden Gate Bridge, California, USA

Keeping fit during the pandemic: A jogger at Golden Gate Bridge, California, USA

First, it's important to note that at time of writing, scientists know relatively little about the so-called "California coronavirus."

There are fears that it may be spreading faster than other strains of coronavirus, that it may lead to more severe cases of infection, requiring more intensive care, and that it may even be more deadly.

But all we have right now — as public information — is from  a pre-print, published on an online platform called medRxiv.

A pre-print is a report or study that, while usually scientific and professional, details only preliminary findings that have yet to be peer-reviewed. That is, the findings have yet to be checked and verified by other groups of scientists.

As such, doctors, for instance, are advised not to use any of the data, as it stands, to make clinical decisions when treating patients.

So, read this as an overview of to-be-confirmed information.

What we know so far

We know that the California coronavirus was first detected in southern parts of the US state. Scientists say it is a variant of SARS-CoV-2, the virus that causes COVID-19.

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But there may be two types of the new variant, both of which have slightly different mutations. The two types are known as B.1.427 and B.1.429. Although in their pre-print study, the authors refer mainly to CAL.20C. 

The researchers are all associated with Cedars-Sinai Medical Center in Los Angeles.

They looked at publicly available data from two clusters or lineages of COVID-19 — known as clades — and found what they call "a relatively novel strain," CAL.20C.

That strain is itself "defined by five concurrent mutations." 

While other novel strains of COVID-19, such as the UK variant, B.1.1.7, have been globally significant for increased infection rates, the researchers write that "there are still no reported strains to account for the spike of cases in Los Angeles and California as a whole, which currently has some of the highest absolute and per-capita COVID transmission rates in the country."

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The UK variant of the coronavirus has spread overseas, despite a "Stay Home, Save Lives" campaign

Until now, it seems. "The predominance of [the CAL.20C] strain coincides with the increased positivity rate seen in this region," they write.

What makes CAL.20C different?

This strain, CAL.20C, was first seen in Los Angeles in July 2020 and then again in southern California in October of last year.

Since then, the strain's prevalence has increased. By December it accounted for 24% of all samples in the Los Angeles area, report the researchers.

Now, this is going to get a bit complicated, so we'll try to simplify.

Those two subgroups or COVID-19 clusters, which we mentioned earlier, are known as 20G and 20C, whereby 20G, is the largest reported clade in North America.

Within those groupings is — one of at least five of mutations — called L452R.

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L452R is a mutation in the virus' spike protein (sometimes known as the "S" protein).

A spike protein is what allows a virus to infect a human cell.

It appears that the new mutation allows the spike protein to attach more easily to a "viral receptor" on the human cell. The receptor is often described as the gateway or entry point through which a virus gets into a cell and infects it.

The L452R spike protein mutation is known to be resistant to certain monoclonal antibodies, which would otherwise stop the virus from infecting a cell. 

That may have implications for patients recovering from a COVID-19 infection or even for people who have been vaccinated.

But the report authors write that the full effect of the CAL.20C mutation, both in terms of its infectiousness and antibody resistance is "unknown at this time." 

A legion of mutations

SARS-CoV-2 has been mutating for as long as we've known of its existence.

The first significant mutation or variant of the virus was described as "D614G" in late January or early February 2020. That quickly substituted the original strain — the strain thought to have caused the late 2019 outbreak in Wuhan, China — and became the dominant strain spreading globally.

Data visualization COVID-19 New Cases Per Capita – 2021-02-24 – global - English

In August or September 2020, Denmark identified a strain in farmed mink.  Danish authorities described that as the "Cluster 5" variant.

By December 2020, it had become clear that variants found in the United Kingdom (variant B.1.1.7) and South Africa (variant B.1.351) were also increasingly dominant — and spreading internationally.

Other variants have been detected in Brazil and Japan.

The situation is made difficult, especially for non-medical experts, as there appears to be no internationally recognized naming convention for all these mutations, as described recently in an article in Nature .

But as the World Health Organization writes: All viruses change over time.

So, perhaps the one clear message to take away from this is that no matter which strain of coronavirus happens to be in your local area, just know it's still out there and that it's worth doing everything we can to protect ourselves and the global community.

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