LOS ANGELES – Los Angeles County scientists have begun to test samples of the coronavirus from local patients to determine if a new, potentially more contagious strain that is circulating in Britain has arrived, as some officials believe is likely amid a major surge of infections.

The variant is a concern because it may make the virus easier to be transmitted from one person to another, officials said. But once a person has the virus, the variant doesn’t appear to make the person more likely to die.

Los Angeles County Public Health Director Barbara Ferrer said a public health laboratory has begun to do gene sequencing to test virus samples collected in L.A. County, but it will take about a week to finish the process.

COVID-19 has been surging out of control in Los Angeles County and other parts of California, overwhelming hospitals and killing more people each day. On Thursday, L.A. County saw its highest number of COVID-19 deaths in a single day: 140.

The spread has been so rapid since Thanksgiving, when many families defied public health guidelines and gathered in large groups, that some have wondered if something about the virus has changed. Officials believe the surge has been worsened by holiday gatherings but are also concerned about other factors, including people going out to shop.

“When I spoke with the state Department of Public Health, they indicated that they’ve been looking and didn’t think they had seen” the new strain, Ferrer told the Los Angeles Times in an interview. “But you know, you have to know what you’re looking for. So I think everyone at this point that’s seeing these kinds of surges is obviously looking to see, ‘Do we have that particular variant?’ “

Los Angeles Mayor Eric Garcetti said a new variant of the coronavirus could be a factor in the recent explosion in coronavirus cases, as well as other factors, including pandemic fatigue, holiday gatherings and winter weather, which may be more conducive to transmission.

“This happened devastatingly quickly. Everybody I talked to said this acceleration was beyond any model and any expectation, so then people say ‘What broke down?’ and I’ve got to think it’s partly the strain that was out there,” Garcetti said in an interview with the Times on Wednesday.

A memo issued by the L.A. County Department of Public Health on Christmas Eve asked labs to review recent data from positive coronavirus tests to be on the lookout for a specific genetic pattern, as well as any unusual molecular patterns.

“Scientists are working to learn more about this variant to better understand how easily it might be transmitted and whether currently authorized vaccines will protect people against it. At this time, there is no evidence that this variant causes more severe illness or increased risk of death or that available vaccines will not be as effective,” the memo said.

Scientists have detected this new coronavirus strain in Europe and South Africa, a discovery that caused a number of countries around the world to announce bans on incoming flights from Britain.

The United States stopped short of a ban, but the U.S. Centers for Disease Control and Prevention said airline passengers from Britain will need to get a negative coronavirus test before their flight.

The discovery of the new strain also caused the British government to institute lockdown measures, including travel restrictions and the shuttering of pubs, gyms, theaters and hair salons, in response to findings that the genetic changes in the new strain could make the virus “up to 70% more transmissible.”

Gov. Gavin Newsom on Monday said that California is testing thousands of virus samples regularly to identify any changes in the virus’ genome. “We haven’t seen anything related to a new strain yet,” Newsom said.

Dr. Mark Ghaly, California’s health and human services secretary, said Monday that the newly identified strain circulating in Britain is essentially “a little bit more sticky than the COVID virus that we’ve been seeing to date.”

“For COVID to enter a human cell, it needs to bind to a receptor, a sort of front door on a human cell,” Ghaly said. “And the new, mutated COVID virus seems to bind a little tighter, a little more easily and enter the cell of the human body easier than our current COVID virus that we have here primarily in California and the United States.”

Both Ghaly and officials in England said the changes make the virus more likely to infect people who are exposed to it. But many other scientists have said there is not yet enough evidence to support this conclusion, and that other factors could just as easily explain the strain’s rapid spread.

The new strain has not shown itself to be more virulent than the conventional version, meaning that it doesn’t necessarily make people sicker. “But the fact that it infects more easily, it seems, is what we are worried about,” Ghaly said.

If the new strain of the virus does get a foothold in California, it’s unclear how it might affect the state’s efforts to contain the outbreak. “The last thing we want to do is let a new strain of COVID come and spread more rapidly or easily across the state,” Ghaly said.

A big concern is that its genetic changes could, in theory, reduce the effectiveness of the COVID-19 vaccines made by Pfizer and Moderna – both of which are being rolled out in the U.S. – as well as three others close behind them.

However, a report last week by British researchers found “no evidence that this variant … will render vaccines less effective.”

Dr. Anthony Fauci, the U.S. government’s top infectious diseases expert, told ABC News on Tuesday he would not be surprised if the strain sparking so much worry in the U.K. has already arrived in the U.S.

“When you have this amount of spread within a place like the U.K. … you really need to assume that it’s here already, and certainly is not the dominant strain, but I would not be surprised at all if it is already here,” Fauci said.