Two studies confirm that a new coronavirus mutant in California is more contagious, although the scale of its threat is unclear.
By Carl Zimmer
A variant first discovered in California in December is more contagious than earlier forms of the coronavirus, two new studies have shown, fueling concerns that emerging mutants like this one could hamper the sharp decline in cases over all in the state and perhaps elsewhere.
In one of the new studies, researchers found that the variant has spread rapidly in a San Francisco neighborhood in the past couple of months. The other report confirmed that the variant has surged across the state, and revealed that it produces twice as many viral particles inside a person’s body as other variants do. That study also hinted that the variant may be better than others at evading the immune system — and vaccines.
“I wish I had better news to give you — that this variant is not significant at all,” said Dr. Charles Chiu, a virologist at the University of California, San Francisco. “But unfortunately, we just follow the science.”
Neither study has yet been published in a scientific journal. And experts don’t know how much of a public health threat this variant poses compared with others that are also spreading in California.
A variant called B.1.1.7 arrived in the United States from Britain, where it swiftly became the dominant form of the virus and overloaded hospitals there. Studies of British medical records suggest that B.1.1.7 is not only more transmissible, but more lethal than earlier variants.
Some experts said the new variant in California was concerning, but unlikely to create as much of a burden as B.1.1.7.
“I’m increasingly convinced that this one is transmitting more than others locally,” said William Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health who was not involved in the research. “But there’s not evidence to suggest that it’s in the same ballpark as B.1.1.7.”
Dr. Chiu first stumbled across the new variant by accident. In December, he and other researchers in California were worried about the discovery of B.1.1.7 in Britain. They began looking through their samples from positive coronavirus tests in California, sequencing viral genomes to see if B.1.1.7 had arrived in their state.
On New Year’s Eve, Dr. Chiu was shocked to find a previously unknown variant that made up one-quarter of the samples he and his colleagues had collected. “I thought that was crazy,” he said.
It turned out that researchers at the Cedars-Sinai Medical Center in Los Angeles separately discovered the same variant surging to high levels in Southern California. Dr. Chiu announced his initial finding, and the Cedars-Sinai team went public two days later.
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