'Mask up, America': Biden signs pandemic mandates for traveling and federal properties
Joe and Jill Biden

In a stark—and according to many public health experts welcome—departure from his mask-averse predecessor, President Joe Biden on Thursday signed an executive order requiring many interstate travelers to wear face coverings in order to help combat the coronavirus pandemic that has now claimed more than 413,000 U.S. lives.

"I'm asking every American to mask up for the next 100 days."
—President Joe Biden

Part of his "100 Days Masking Challenge," Thursday's executive order followed another on Wednesday—the very first of Biden's presidency—mandating masks on federal properties and directing federal agencies to comply with U.S. Centers for Disease Control and Prevention guidelines on mask-wearing and social distancing.

"I'm asking every American to mask up for the next 100 days," Biden said at the White House Thursday. "The mask has become a partisan issue, unfortunately. But it's a patriotic act... [Masks] are the single-best thing to do, even more important than vaccines, because they take time to work."

"The experts say that by wearing a mask from now until April, we'd save more than 50,000 lives," he added.

The travel order covers planes, trains, ferries, intercity buses, and public transportation. Additionally, it requires people visiting the United States from other countries to produce proof of a recent negative Covid-19 test and "comply with other applicable CDC guidelines concerning international travel, including recommended periods of self-quarantine or self-isolation after entry into the United States."

Epidemiologists overwhelmingly concur that concerted efforts to implement and enforce mask-wearing guidelines could lead to a significant reduction in coronavirus cases.

Dr. Chris Beyrer, a professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health in Baltimore, told TODAY earlier this week that widespread mask-wearing for 100 days could do a "great deal" to lower virus transmission rates.

"We have ongoing high levels of community transmission all over this country," said Beyrer. "With that rate of community transmission, with the infectiousness of this virus, and with the weather that we're dealing with... consistent mask-wearing could have a major impact on reducing community transmission."

Dr. Ali Mokdad, an epidemiologist at the Institute for Health Metrics and Evaluation at the University of Washington, called masks "in some ways our best medical tool."

"[Masks] can save hundreds of thousands of lives without the need for surgery, drugs; no side effects, and readily available to everyone," Mokdad told the Washington Post.

Many transportation workers also welcomed the new rules.

"What a difference leadership makes!" said Sara Nelson, president of the Association of Flight Attendants-CWA International, in a CNN interview. "We welcome President Biden's nationwide approach to crushing the virus and lifting us out of this pandemic."

It is unclear when the orders will take effect, or how or even if they will be enforced. It is also not known whether masks will be required at outdoor federal properties such as national parks.

On Friday, Dr. Anthony Fauci, Biden's chief medical adviser, told CNN that former President Donald Trump's lies and downplaying of the coronavirus pandemic "very likely" cost lives.

"Particularly when you're in the situation... with the number of cases and hospitalizations and deaths that we have—when you start talking about things that make no sense medically and no sense scientifically, that clearly is not helpful," said Fauci, who also served under—but was increasingly sidelined by—Trump.

Fauci's comments came as Johns Hopkins University's Coronavirus Resource Center reported nearly 24.8 million confirmed U.S. Covid-19 infections and nearly 413,600 deaths.