An international team of 13 scientists researching the origins of COVID-19 arrived Thursday in Wuhan, China, where the novel coronavirus was first discovered, according to the World Health Organization.

"The experts will begin their work immediately during the 2 weeks quarantine protocol for international travelers," the WHO wrote on Twitter.

All team members had to be tested for COVID-19 again in Singapore before flying to China. The polymerase chain reaction (PCR) tests were all negative, but two IgM antibody tests returned positive results. Those two scientists remain in Singapore as they are retested, according to the WHO.

A total of 965,000 workers in the United States filed jobless claims last week, the U.S. Department of Labor said Thursday, an increase of 181,000 from the prior week.

The Labor Department also said that more than 18 million people were still receiving some form of unemployment benefits through all government programs for the week ending Dec. 26. For the comparable week in 2019, that figure was just above 2 million.

The weekly unemployment tally has fallen since peaking at 6.9 million in March but still remains elevated by historical standards.

The pre-pandemic record for weekly unemployment filings was 695,000 in 1982.

That record has been broken every week since late March.

As of last month, the unemployment rate in the U.S. was 6.7%. It was 3.5% last February.

-ABC News’ Catherine Thorbecke contributed to this report

This week’s national ensemble forecast released by the U.S. Centers for Disease Control and Prevention predicts that 16,200 to 29,600 more Americans will likely die from COVID-19 in the week ending Feb. 2.

The national ensemble estimates a total of 440,000 to 477,000 deaths from the disease will be reported nationwide by that date.

Nearly all U.S. metro areas with over 500,000 people are in "full resurgence" of COVID-19, the White House coronavirus task force said in its latest report, obtained by ABC News Wednesday.

In the report, dated Jan. 10, the task force said the fall/winter surge has had nearly twice the rate of rise in COVID-19 cases as the spring and summer surges.

Several states, including Arizona, California, Florida, Georgia, Louisiana, New Mexico and South Carolina, are also in "full pandemic resurgence," the report stated.

Only "aggressive mitigation" can "match a more aggressive virus," and Americans must take more precautions, "moving beyond what worked in the summer to more layered mitigation," the report stated.

The task force recommended uniform mask implementation and "strict physical distancing." Without that, "epidemics could quickly worsen as more transmissible variants spread and become predominant," it warned.

ABC News' Josh Margolin and Brian Hartman contributed to this report.

Pope Francis and his predecessor, Pope Emeritus Benedict XVI, have received their first dose of a COVID-19 vaccine, according to Vatican spokesman Matteo Bruni.

"I can confirm that as part of the Vatican City State vaccination program to date, the first dose of the COVID-19 vaccine has been administered to Pope Francis and the Pope Emeritus," Bruni said in a statement Thursday.

Francis, who turned 84 last month and had part of a lung removed when he was younger, reportedly received the shot Wednesday while Benedict, 93, reportedly got it Thursday.

Vatican City, an independent enclave surrounded by Rome that serves as the headquarters of the Roman Catholic Church, launched the immunization campaign on Wednesday, administering doses of a COVID-19 vaccine developed by U.S. pharmaceutical giant Pfizer and its German partner BioNTech.

The tiny city-state has a population of only around 800 people but employs more than 4,000. It's unclear how many doses of the Pfizer/BioNTech vaccine have been procured so far.

Vatican City citizens, along with employees and pensioners, will have the opportunity to receive the vaccine as well as family members who are entitled to use of the city-state's health care system. Priority is being given to health care workers, public safety personnel, the elderly and individuals who are most frequently in contact with the public, according to Bruni.

The vaccination campaign is voluntary and people under the age of 18 are being excluded for the time being, Bruni said.

Since the start of the pandemic, Vatican City has reported at least 27 confirmed cases of COVID-19, according to a real-time count kept by Johns Hopkins University.

ABC News' Phoebe Natanson contributed to this report.