The U.S. death toll from COVID-19 continues to climb in the weeks following the end-of-year holidays. Fatalities from the disease nationwide are currently 25% higher than at any other time during the coronavirus pandemic, according to The COVID Tracking Project, a volunteer-run effort to track the U.S. outbreak.

"For scale, COVID-19 deaths reported this week exceed the CDC's estimate of 22K flu-related deaths during the entire 2019-2020 season," The COVID Tracking Project wrote on Twitter Thursday.

There were 3,915 deaths from COVID-19 registered nationwide on Thursday, well above a seven-day average that continues to rise. However, COVID-19 cases and hospitalizations were under the seven-day average on Thursday.

The one bit of good news highlighted by The COVID Tracking Project was that hospitalizations are leveling off. Still, there are 128,947 people currently hospitalized with COVID-19 in the United States, much more than at any other time during the pandemic.

The COVID Tracking Project singled out Alabama, Arizona, California and Florida as particularly concerning locations right now. Arizona currently has the worst per-capita case numbers in the world, according to the project.

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.

There were 229,610 new cases of COVID-19 confirmed in the United States on Wednesday, according to a real-time count kept by Johns Hopkins University.

It's the ninth straight day that the country has reported more than 200,000 new cases. Wednesday's tally is less than the country's all-time high of 302,506 newly confirmed infections on Jan. 2, Johns Hopkins data shows.

An additional 3,959 new deaths from COVID-19 were registered nationwide on Wednesday, down from a peak of 4,327 fatalities logged the previous day, according to Johns Hopkins data.

COVID-19 data may be skewed due to possible lags in reporting over the holidays followed by a potentially very large backlog.

A total of 23,079,163 people in the U.S. have been diagnosed with COVID-19 since the pandemic began, and at least 384,794 have died, according to Johns Hopkins data. The cases include people from all 50 U.S. states, Washington, D.C., and other U.S. territories as well as repatriated citizens.

Much of the country was under lockdown by the end of March as the first wave of pandemic hit. By May 20, all U.S. states had begun lifting stay-at-home orders and other restrictions put in place to curb the spread of the novel coronavirus. The day-to-day increase in the country's cases then hovered around 20,000 for a couple of weeks before shooting back up over the summer.

The numbers lingered around 40,000 to 50,000 from mid-August through early October before surging again to record levels, crossing 100,000 for the first time on Nov. 4, then reaching 200,000 on Nov. 27 before topping 300,000 on Jan. 2.