A World Health Organization team emerged from their 14-day quarantine in the Chinese city of Wuhan on Thursday to begin field work in their investigation of the origins of the virus that cause the COVID-19 pandemic.

China's COVID-19 regulations required all members of the team to complete 14 days of quarantine upon their arrival. They have been taking part in virtual meetings during the quarantine period.

The researchers were seen leaving their hotel and boarding a bus on Thursday afternoon.

ABC News' Karson Yiu contributed to this report.

There were 152,478 new cases of COVID-19 confirmed in the United States on Wednesday, according to a real-time count kept by Johns Hopkins University.

Wednesday's case count is far less than the country's all-time high of 300,282 newly confirmed infections on Jan. 2, Johns Hopkins data shows.

An additional 3,943 fatalities from COVID-19 were registered nationwide on Wednesday, down from a peak of 4,466 new deaths on Jan. 12, according to Johns Hopkins data.

COVID-19 data may be skewed due to possible lags in reporting over the Martin Luther King Jr. Day holiday weekend.

A total of 25,598,062 people in the U.S. have been diagnosed with COVID-19 since the pandemic began, and at least 429,195 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.

So far, the U.S. Food and Drug Administration has authorized two COVID-19 vaccines for emergency use -- one developed by U.S. pharmaceutical giant Pfizer and its German partner BioNTech, and another developed by American biotechnology company Moderna and the National Institute of Allergy and Infectious Diseases. More than 24 million vaccine doses have been administered nationwide, according to the latest data from the Centers for Disease Control and Prevention.

A draft request for assistance between the Federal Emergency Management Agency and the U.S. Department of Defense is under discussion that would seek as many as 10,000 service members to support administering COVID-19 vaccine shots up at 100 sites nationwide, according to a FEMA official who spoke on condition of anonymity because the details were not final.

A defense official, who also spoke on condition of anonymity, confirmed discussions are under way, but the final number of personnel is not settled.

It is also unclear what kind of active duty or National Guard mix it could be, and whether it includes National Guardsmen already helping in the vaccine effort around the country.

ABC News' Matthew Vann and Luis Martinez contributed to this report.

Dr. Anthony Fauci, chief medical adviser to U.S. President Joe Biden, told Fox News' "America Reports With John Roberts & Sandra Smith" that there’s no official recommendation yet on wearing double masks.

"The CDC doesn't officially recommend wearing double masks," Fauci said. "You know what would be a good start? If everybody wears at least one mask."

ABC News’ Anne Flaherty contributed to this report.

The United Kingdom now has the highest COVID-19 transmission and death rates of any country in the world, according to the World Health Organization's weekly epidemiological report released Wednesday.

With 383.1 new cases of COVID-19 per 100,000 residents, the U.K.'s transmission rate is higher than that of the United States, which decreased by 20% over the previous week to 380.6 new cases per 100,000 residents. But the UK appears to be moving in the right direction -- this week showed a 24% decrease in new cases confirmed from the previous week, the report said.

The U.K.'s COVID-19 death rate is also the world's highest, with 12.9 fatalities from the disease per 100,000 residents. The country -- which is made up of England, Scotland, Wales and Northern Ireland -- saw a 13% increase in new deaths over the previous week, according to the report.

In the U.S., the COVID-19 death rate went down by 7% to 6.5 fatalities per 100,000 residents, the report said.

As of Monday, 70 countries have detected cases of a new, more contagious variant of the novel coronavirus that was first identified in the U.K., while 31 nations have cases of another variant that first emerged in South Africa and eight countries have cases of a variant that was first identified in Brazil, according to the report.

ABC News’ Christine Theodorou contributed to this report.