The coronavirus variant first seen in Los Angeles in July is now responsible for about 44% of new infections in Southern California and more than a third of new infections in the state, researchers reported Thursday.
In addition, the variant has spread across the United States and to six countries around the world, according to the study in the Journal of the American Medical Assn.
It “ remains uncertain ” whether the genetic changes that characterize the fast-moving variety improved its ability to transmit from person to person or made people infected with it sicker, acknowledged a team from Cedars-Sinai Medical Center in Los Angeles in the JAMA report. But the rapid spread of the virus in California is of some concern, they wrote.
The native variant is distinct from other versions of the virus present in the US, including the B.1.1.7 strain from the United Kingdom and the B.1.351 strain from South Africa. But like those new strains, this variant is determined by various mutations in the virus’s spike protein, the “coupling mechanism” the virus uses to adhere to human cells.
One of five mutations of the California variant, known to scientists as L452R, could alter a particularly critical portion of the spike protein, the receptor binding domain.
A study conducted last year by Howard University researchers found that the mutation helps the virus attach more tightly to human cells. It therefore has the potential to enhance the transmission of the virus.
Samples of the new variant are being tested at both Cedars-Sinai and the UC San Francisco Medical Center in an attempt to find out if the altered genetic makeup has given the virus new powers to spread or become ill.
“New variants don’t always affect the behavior of a virus in the body,” said Dr. Eric Vail, one of the study’s senior authors.
But because this one took flight amid a disastrous wave of new infections in Southern California, and because three out of five changes in the genetic code involve the spike protein, it’s of particular concern, said Vail, a molecular pathologist in Cedars-Sinai’s Department of Pathology and Laboratory Medicine.
The rapidly increasing proportion of California cases is also ominous, the study authors said.
While the variant was barely detectable in early October, it accounted for 24% of the approximately 4,500 viral samples collected in Southern California in the last weeks of 2020, and 18% of samples statewide. Less than a month later, the proportion of new infections had risen.
From Jan. 1 to Jan. 22, the variant accounted for 44% of the coronavirus samples collected in Southern California and 35% of the samples from the entire state.
When assessing the likely impact of emerging variants elsewhere, scientists have seen trends like this one as evidence that a new genetic variant has gained a competitive advantage over others already in circulation. One explanation for this is an increase in transferability.
‘If you look at the numbers, they suggest it [the California variant] is probably more contagious, ”said Jasmine Plummer, a cedar Sinai researcher who led the study with Vail. But because other factors may have contributed to the growing presence, “we need to do more studies” to confirm the suspicion, she warned.
Shaolei Teng, a Howard University biologist who led a team that examined the effect of the virus’s genetic changes, said the variant’s L452R mutation clearly improved its ability to bind to human cells. In all likelihood, he said, the change also makes it easier for the virus to get into the cells – a critical step in the replication process.
The mutation is “beneficial to the virus and may be the reason it has become dominant in California,” Teng said.
In addition, the variant is starting to travel widely. It has been detected in Alaska, Arizona, Connecticut, Georgia, Hawaii, Maryland, Michigan, New Mexico, Nevada, New York, Oregon, Rhode Island, South Carolina, Texas, Utah, Washington, Wisconsin, Wyoming, and Washington, DC
It has also made its way to Australia, Denmark, Israel, New Zealand, Singapore, and the United Kingdom.
“The emergence of these and other new variants is likely to be a common occurrence until the spread of this virus is reduced,” a team from the National Institute of Allergy and Infectious Diseases wrote in an editorial accompanying the study. “This highlights the importance of a global approach to surveillance, tracking and vaccine deployment.”
Plummer said Southern California travelers likely carried the new variant with them to other states and countries.
Los Angeles International Airport has long been one of the busiest travel hubs in the US and is ranked No. 2 in total passengers boarding in 2019 according to the US Department of Transportation. It is an important gateway to a number of foreign destinations, including Australia and New Zealand.
While US air traffic plummeted during the pandemic, more than 4 million domestic and international passengers still traveled through LAX in November and December, according to Los Angeles World Airports, which operate the airport.