The Centers for Disease Control and Prevention issued a federal transportation mask mandate Friday night which will be effective starting Feb. 1.

The mandate states that people traveling within or out of the United States must wear face masks while on conveyances and at transportation hubs to prevent the spread of COVID-19.

This includes airplanes, ships, ferries, trains, subways, buses, taxis and ride-shares, as well as subway stations, airports and other transportation hubs.

Drivers, conductors, and other workers involved in the operation of conveyances must also wear masks at all times, the CDC says.

"Conveyance operators must also require all persons onboard to wear masks when boarding, disembarking, and for the duration of travel," the mandate states. "Operators of transportation hubs must require all persons to wear a mask when entering or on the premises of a transportation hub."

There have been more COVID-19 cases reported globally in the past two weeks than during the first six months of the pandemic, according to the World Health Organization.

Almost exactly a year ago, there were fewer than 100 confirmed cases of the virus outside of China, WHO Director-General Dr. Tedros Adhanom Ghebreyesus noted during a media briefing Friday. This week, the number of reported cases globally surpassed 100 million.

"Now, vaccines are giving us another window of opportunity to bring the pandemic under control. We must not squander it," Tedros said.

At the same time, Tedros warned that vaccine hoarding will be a "catastrophic moral failing" that will ultimately "keep the pandemic burning" and hinder economic recovery.

His comments come after the European Union publicly fought with AstraZeneca this week over how many doses it can expect of the drugmaker's COVID-19 vaccine. After regulators approved the vaccine Friday, the EU enacted an export restriction on doses produced in the bloc. WHO officials called the move "concerning" and part of a "worrying trend."

"Vaccine nationalism might serve short-term political goals, but it's ultimately short-sighted and self-defeating. We will not end the pandemic anywhere until we end it everywhere," Tedros said. "My message to governments is to vaccinate your health workers and older people, and share excess doses with COVAX, so other countries can do the same."

ABC News' Kirit Radia contributed to this report.

The CDC is extending its moratorium on housing evictions through March 31, citing the health threat it poses.

The order had been set to expire on Jan. 31.

“Keeping people in their homes and out of congregate settings -- like shelters -- is a key step in helping to stop the spread of COVID-19,” the CDC said in a statement.

ABC News’ Anne Flaherty contributed to this report.

At Friday’s White House press briefing, Dr. Anthony Fauci said the United Kingdom variant will likely become more “dominant” in the U.S. toward the end of March or early April.

There are 379 confirmed cases across 29 states of the B117 strain of the coronavirus, according to CDC director Dr. Rochelle Walensky.

Fauci indicated that the evolving nature of the virus is something the medical community will have to continue dealing with going forward.

“Even though the long-range effect in the sense of severe disease is still handled reasonably well by the vaccines, this is a wake-up call to all of us, that we will be dealing, as the virus uses its devices to evade pressure, particularly immunological pressure, that we will continue to see the evolution of mutants,” he said.

Fauci also indicated that the fight to contain the new variants will impact the vaccine response.

“We, as a government, the companies, all of us that are in this together, will have to be nimble to be able to just adjust readily to make versions of the vaccine that actually are specifically directed towards whatever mutation is actually prevalent at any given time,” he said.

ABC News’ Matthew Vann contributed to this report.

Dr. Anthony Fauci, chief medical adviser to U.S. President Joe Biden and the nation's leading infectious disease expert, said Americans can expect to see more COVID-19 vaccine doses available throughout the country in the coming weeks.

"As we get into February, March and April, we're going to see an escalation of availability of doses that we may have not had a week or two or three ago," Fauci, who is also the director of the National Institute of Allergy and Infectious Diseases, told ABC News chief anchor George Stephanopoulos Thursday on "Good Morning America."

Although COVID-19 data is starting to show some promising trends, Fauci said the U.S. outbreak is "still a very serious situation."

"If you look throughout the country, the dynamics of the outbreak are a little bit unstable," he noted, "even though for the most part we're seeing general trends, seven-day trends of cases going down and ultimately, hopefully, hospitalizations and deaths."

When asked about reopening schools safely, Fauci said COVID-19 transmission rates in schools actually appear to be less than in communities when the schools have the resources and protection they need.

"So if you have a situation where you have dynamics of a viral spread in a community, it's less likely that the children who are in the school -- if we do things right, it's less likely that they're going to get infected," he said. "Obviously we want to get the teachers vaccinated, we want to make sure they have the resources to do it correctly. But when you look at the history of how this virus is moving in schools, it seems to be less spreading there than it is in the community."

Fauci also expressed concern over the new, more contagious variant of the novel coronavirus that was first identified in South Africa and has since spread to dozens of other nations, including the United States.

"The one in South Africa, George, troubles me," he said, explaining that lab experiments show the neutralizing antibodies induced by existing COVID-19 vaccines are "diminished by multifold" when tested against the South Africa variant, called B1351.

"It's still within the range of what you would predict to be protective," he added, "but I take no great comfort in that."

However, scientists are already working on vaccines that will specifically target the South Africa strain, according to Fauci.

"May not be necessary," he said, "but if it is we'll already be on the road to be able to give people a boost that directs against the South African isolate."