DENVER (AP) — A new variant of the coronavirus that may be more contagious has been found in a Colorado man who had not been traveling, triggering a host of questions about how the first reported U.S. case of the new version showed up in the Rocky Mountain state.

The new variant was first identified in England, and infections are soaring now in Britain, where the number of hospitalized COVID-19 patients has surpassed the first peak of the outbreak in the spring. The new variant has also been found in several other countries.

Colorado officials were expected to provide more details at a news conference Wednesday about how the man in his 20s from a mostly rural area of rolling plains at the edge of the Denver metro area came down with the variant. Gov. Jared Polis announced the case Tuesday, adding urgency to efforts to vaccinate Americans.

For the moment, the variant is likely still rare in the U.S., but the lack of travel history in the first case means it is spreading, probably seeded by travelers from Britain in November or December, said scientist Trevor Bedford, who studies the spread of COVID-19 at Fred Hutchinson Cancer Research Center in Seattle.

“Now I’m worried there will be another spring wave due to the variant,” Bedford said. “It’s a race with the vaccine, but now the virus has just gotten a little bit faster.”

The man is in isolation southeast of Denver in Elbert County, state health officials said.

Colorado Politics reported there is a second suspected case of the variant in the state according to Dwayne Smith, director of public health for Elbert County. Both of the people were working in the Elbert County community of Simla. Neither is a resident of that county — expanding the possibility that the variant has spread in the state.

Public health officials are investigating other potential cases of the variant, which was confirmed by the Colorado State Laboratory, and performing contact tracing to determine its spread.

Scientists in the United Kingdom believe the variant is more contagious than previously identified ones — though they have found no evidence that it is more lethal or causes more severe illness. Experts also believe the vaccines being given now will be effective against the variant.

Still, authorities in Britain have blamed the variant for a spike in hospitalizations since a higher rate of transmission increases the likelihood that more people will become very ill.

Amid the strain on its hospitals, Britain announced Wednesday that it would prioritize giving a single dose of the newly authorized AstraZeneca vaccine to as many people as possible. The vaccine was tested with two doses a few weeks apart, but one dose is believed to give a large measure of protection against the virus. The British government now plans to give everyone a second shot about 12 weeks later.

It’s not clear exactly why the new variant appears to spread faster. It has an unusually large number of genetic changes, or mutations, particularly in areas that affect the Spike protein, according to reports by Public Health England.

“There is a lot we don’t know about this new COVID-19 variant, but scientists in the United Kingdom are warning the world that it is significantly more contagious. The health and safety of Coloradans is our top priority, and we will closely monitor this case, as well as all COVID-19 indicators, very closely,” Polis, the Colorado governor, said.

The discovery of the new variant led the Centers for Disease Control and Prevention to issue new rules on Christmas Day for travelers arriving to the U.S. from the U.K., requiring they show proof of a negative COVID-19 test.

Worry has been growing about the variant, known as B.1.1.7, since the weekend before Christmas, when Britain’s prime minister said the new variant was moving rapidly through southeast England.

Dozens of countries barred flights from the U.K., and southern England was placed under strict lockdown measures. Scientists say there is reason for concern but the new strains should not cause alarm.

Japan announced Monday it would bar entry of all nonresident foreign nationals as a precaution against the new variant.

New versions of the coronavirus have been seen almost since the virus was first detected in China nearly a year ago. It is common for viruses to undergo minor changes as they reproduce and move through a population. The slight modifications are how scientists track the spread of a virus from one place to another.

But if the virus has significant mutations, one concern is that current vaccines might no longer offer the same protections. Although that’s a possibility to watch for over time with the coronavirus, experts say they don’t believe it will be the case with the latest variant.

South Africa has also discovered a highly contagious COVID-19 variant that is driving the country’s latest spike of confirmed cases, hospitalizations and deaths. The variant, known as 501.V2, is dominant among the newly confirmed infections in South Africa, according to health officials and scientists leading the country’s virus strategy.

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AP Medical Writer Carla K. Johnson in Washington state contributed.

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Nieberg is a corps member for the Associated Press/Report for America Statehouse News Initiative. Report for America is a nonprofit national service program that places journalists in local newsrooms to report on undercovered issues.

NASHVILLE, Tenn. (AP) — More than a year before Anthony Warner detonated a bomb in downtown Nashville on Christmas, officers visited his home after his girlfriend told police that he was building bombs in an RV trailer at his residence, according to documents obtained by The Associated Press. But they were unable to make contact with him, or see inside his RV.

Officers were called to Pamela Perry’s home in Nashville on Aug. 21, 2019, after getting a report from her attorney that she was making suicidal threats while sitting on her front porch with firearms, the Metropolitan Nashville Police Department said Tuesday in an emailed statement. A police report said Raymond Throckmorton, the attorney, told officers that day that he also represented Warner.

When officers arrived at Perry’s home, police said she had two unloaded pistols sitting next to her on the porch. She told them those guns belonged to “Tony Warner,” police said, and she did not want them in the house any longer. Perry, then 62, was then transported for a psychological evaluation after speaking to mental health professionals on the phone.

Throckmorton told The Tennessean that Perry had fears about her safety, and thought Warner may harm her. The attorney was also at the scene that day, and told officers Warner “frequently talks about the military and bomb making,” the police report said. Warner “knows what he is doing and is capable of making a bomb,” Throckmorton said to responding officers.

Police then went to Warner’s home, located about 1.5 miles (2.4 kilometers) from Perry’s home, but he didn’t answer the door when they knocked several times. They saw the RV in the backyard, the report said, but the yard was fenced off and officers couldn’t see inside the vehicle.

The report said there also were “several security cameras and wires attached to an alarm sign on the front door” of the home. Officers then notified supervisors and detectives.

“They saw no evidence of a crime and had no authority to enter his home or fenced property,” the police statement said.

After officers visited Warner’s home last August, the police department’s hazardous devices unit was given a copy of the police report. During the week of August 26, 2019, they contacted Throckmorton. Police said officers recalled Throckmorton saying Warner “did not care for the police,” and that he wouldn’t allow Warner “to permit a visual inspection of the RV.”

Throckmorton disputes that he told police they couldn’t search the vehicle. “I have no memory of that whatsoever,” he told The Tennessean. “I didn’t represent him anymore. He wasn’t an active client. I’m not a criminal defense attorney.”

Throckmorton told the newspaper he represented Warner in a civil case several years ago, and that Warner was no longer his client in August 2019. “Somebody, somewhere dropped the ball,” he said.

A day after officers visited Warner’s home, the police report and identifying information about Warner were sent to the FBI to check their databases and determine whether Warner had prior military connections, police said.

Later that day, the police department said “the FBI reported back that they checked their holdings and found no records on Warner at all.” FBI spokesperson Darrell DeBusk told The Tennessean the agency had conducted a standard agency-to-agency record check.

Six days later, “the FBI reported that Department of Defense checks on Warner were all negative,” the police department said.

No other information about Warner came to the department or the FBI’s attention after August 2019, police said. “At no time was there any evidence of a crime detected and no additional action was taken,” the statement said. “The ATF also had no information on him.”

Warner’s only arrest was for a 1978 marijuana-related charge.

The bombing happened on Christmas morning, well before downtown streets were bustling with activity. Police were responding to a report of shots fired Friday when they encountered the RV blaring a recorded warning that a bomb would detonate in 15 minutes. Then, for reasons that may never be known, the audio switched to a recording of Petula Clark’s 1964 hit “Downtown” shortly before the blast. Dozens of buildings were damaged and several people were injured.

Investigators have not uncovered a motive for the Christmas day bombing nor was it revealed why Warner had selected the particular location, which damaged an AT&T building and wreaked havoc on cellphone, police and hospital communications in several Southern states as the company worked to restore service. The company said on Monday the majority of services had been restored for residents and businesses.