More dangerous strain prompts worries mutations will slow progress vs. virus

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 overall in the state and perhaps elsewhere.

In one of the studies, researchers found that the variant has spread rapidly in a San Francisco neighborhood in the past couple of months. The other report confirmed the variant has surged across the state and revealed it produces twice as many viral particles inside a person’s body as other variants do. That study also hinted 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 virus expert 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 do not 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 also 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, a public health researcher 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.”