The California Covid variant is 11 times more deadly than the South Africa strain, a study claims.
The concerning mutation, which was homegrown and identified in the US, is officially known as B.1.427/B.1.429 and can be added to a growing list of new strains.
Other highly contagious variants include the one found in Kent, which subsequently surged through Britain and saw England thrust into a third lockdown in January.
While those in South Africa and Brazil have also created major cause for concern, with experts desperately working to contain potential further mutations.
The California strain, which has not made it to the UK, is thought to drive a viral load twice as high as the original one found in Wuhan, China, in 2019, into those infected, according to a new study from the University of California, San Francisco (UCSF).
A higher viral load could mean a patient is especially contagious and therefore more easily able to spread the virus, though this is still being monitored.
Researchers there also suggest it spreads at least as quickly as other recent mutations and could be 11 times more fatal.
It was first identified in May last year, but remained largely non-existent until October.
In the study, due to be posted to medRxiv.org in the coming days, scientists took 2,172 samples of the strain from across the state between September 2020 and January 2021, reports the Daily Mail.
By last month, the US mutation accounted for over half of all genetically analysed Covid samples in that part of the country.
While a scientist working on the UCSF study told the Los Angeles Times it could account for 90 percent of all California’s infections by the end of March.
UCSF professor of laboratory medicine and infectious diseases Dr Charles Chiu also told the newspaper it maybe more transmissible than other strains by up to 24 percent.
Furthermore, people who have overcome the California variant appear to have produced two-fold lower antibodies, the research suggests.
Dr Chiu and his team found an 11-fold higher death rate, however, there were only 12 deaths in the group, meaning it could be a “statistical fluke” and would need to be tested within a bigger pool, experts told the Times.
It should also be noted, that while examples of the variant have been found in other US states, it has only surged in California.