A newly identified variant of the virus that causes COVID-19 may have emerged in the U.S. in May and could be one of the predominant versions circulating now, researchers at Southern Illinois University found.

Just because a new variant has emerged doesn't mean it's inherently dangerous, experts cautioned. It’s unknown if this new U.S. variant is more transmissible and deadly, but scientists say they are monitoring and continuing to study newly emerging viral variants. On Wednesday, researchers at Ohio State reported two newly identified ones. On Thursday, researchers at Southern Illinois University said they also identified a new variant, which is likely the same as the two identified in Ohio.

Now, researchers at Southern Illinois University are sharing even more details about this U.S. variant, which they are calling 20C-US. Origins of this variant can be traced to May 2020 from a sample in Texas, they said. 

The 20C-US variant appears to be widespread in the Upper Midwest and comprises roughly 50% of the samples in the U.S., said Keith T. Gagnon, coauthor of the study and associate professor at Southern Illinois University. 

"Let’s not get overly excited -- but be diligent," Gagon said. "Here it was, underneath our noses, for months."

“It doesn't look like it’s going to get in the way of vaccines," Gagnon added. 

ABC News’ Sean Llewellyn, Eric Strauss and Sony Salzman contributed to this report.

Texas, home to about 29 million people, has become the first U.S. state to administer more than 1 million vaccine doses, Gov. Greg Abbott said.

Texas has 2,040,751 confirmed cases and at least 31,277 fatalities, according to real-time data collected by Johns Hopkins University.

Texas’ Harris County, home to Houston, ranks No. 5 in the country for the highest number of confirmed cases, behind Los Angeles County, California; Cook County, Illinois; Marciopa County, Arizona; and Miami-Dade County, Florida.

ABC News’ Gina Sunseri contributed to this report.

The United Kingdom will ban arrivals from several South and Central American countries beginning Friday, following evidence of a new variant of the novel coronavirus from Brazil, British Transport Secretary Grant Shapps announced Thursday.

The U.K. government will ban arrivals from Argentina, Brazil, Bolivia, Cape Verde, Chile, Colombia, Ecuador, French Guiana, Guyana, Panama, Paraguay, Peru, Suriname, Uruguay and Venezuela, according to Shapps.

Travel from Portugal to the U.K. will also be suspended given its strong travel links with Brazil, Shapps said.

ABC News’ Christine Theodorou contributed to this report.

About one in every three people in Los Angeles County has been infected with COVID-19 since the beginning of the pandemic, Los Angeles County Health Department officials said Wednesday.

Los Angeles County is close to becoming the county to reach 1 million cases. As of Thursday morning, 958,497 people in the county had been infected.

ABC News’ Bonnie Mclean contributed to this report.