A new Covid-19 variant originating from California could be more contagious and could cause more severe disease, scientists have warned.What is the evidence for the California strain being more dangerous?
The new variant could be more efficient at docking to cells, increasing its infectiousness, due to a mutation that affects the spike protein - University of California, San Francisco researcher Dr Charles Chiu told CNN.
His team reviewed 308 Covid cases in San Francisco and found a higher percentage of people died from the California variant, the New York Times reported. But he warned the findings may not hold up in a larger sample.
Experiments also showed the new variant was at least 40% more effective at infecting human cells and Dr Chiu's team found that people infected with the variant produced a viral load twice as large as that of other variants.
Will existing vaccines work against the new strain?
According to lab experiments by the University of California, San Francisco, antibodies from people who recovered from infections from other variants were less effective at blocking the new variant.
But researchers do not yet know if the existing vaccines will be less effective against the California variant.
What is the evidence for the variant being more contagious?
The university also found that the new strain has spread rapidly in San Francisco's Mission District.
More than 8,000 people in the district were tested throughout January and researchers found more than half of positive tests were of the new variant, a significant increase from 16% back in November.
Separately, Cedars Sinai Medical Centre in Los Angeles found the variant was in nearly half of Southern California Covid cases and was detected in 19 US states and six other countries - including the UK. The information is true as of January 22.
According to the medical centre, the B.1.427/B.1.429 strain was first discovered in July 2020 in one case in Los Angeles. It reemerged in October in Southern California and quickly spread in November and December.
Travellers appeared to be carrying the variant from Southern California to other states and abroad, according to Cedars-Sinai research scientist Jasmine Plummer.
She said earlier this month: "CAL.20C is moving, and we think it is Californians who are moving it."
What are the arguments against it being more contagious?
Dr William Hanage, of Harvard, told the New York Times he does not think the B.1.427/B.1.429 variant is "as big a deal as the others", such as the Kent variant, known as B.1.1.7.
Dr Chiu's team estimate that the variant originated in late spring last year.
If this is correct, Dr Hanage says the variant may have lurked at extremely low levels for four months or more.
He suggested that variants might be everywhere and "we’re just seeing them at the places where there’s sequencing.”
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