Health experts and scientists think you should wear a mask, and the state health department recommends it. But those opinions and recommendations could become mandates if Spokane County Health Officer Dr. Bob Lutz follows King County’s lead in the coming weeks.

Starting Monday, King County residents must wear face masks in indoor public settings as well as in outdoor settings where physical distancing of 6 feet is not possible.

“There’s a very strong likelihood that we will do something similar in the next week or two,” Lutz said on Tuesday.

Spokane Mayor Nadine Woodward said Tuesday she would support a public mask requirement “if that is the best practice and protocol suggested by our health officer.”

Woodward said she often wears a mask in public and that new norms are “something that we all have to start getting used to.”

King County Health Officer Dr. Jeff Duchin issued the directive mandating face coverings earlier this week, when he also directed businesses to post signs advising customers to wear masks.

The King County directive applies to grocery stores, pharmacies, commercial retail stores, restaurants and public transportation. Residents are asked to not use medical-grade masks or N95 respirators, so those supplies can be saved for health care workers. Instead they should use cloth face coverings that cover both the nose and mouth.

Wearing face masks does not replace social distancing, and the King County directive makes note of this, encouraging residents to continue to physically distance whenever they can.

But why face masks? Do they actually work?

Research shows masking is an effective way to significantly lower transmission of the virus that causes COVID-19, SARS-CoV-2, which is transmitted through respiratory droplets that leave a person’s mouth while talking, coughing or sneezing.

Masking works best when there is near-universal adoption.

Researchers who modeled the effectiveness of masking found that when both 50% of the population and 80 to 90% of the population practiced social distancing and masking with no lockdown, it would result in a “substantial reduction of infection.”

On the contrary, not wearing a mask can lead to more community spread of COVID-19.

“Without masking, lifting lockdown after nine weeks while keeping social distancing measures will risk a major second wave of the epidemic in 4-5 months’ time,” scientists warn in a study, based on their model published last month.

A group called Masks 4 All is tracking which states and countries require universal masking. By their count, 19 states, including Washington, have no mask requirements. Countries that do require universal masking, along with other nonpharmaceutical interventions, appear to have contained major COVID-19 outbreaks so far.

When George Gao, the director of the Chinese Center for Disease Control and Prevention was asked what mistakes other countries are making in responding to the pandemic, he told Science that “the big mistake in the U.S. and Europe, in my opinion, is that people aren’t wearing masks.”

He added, “This virus is transmitted by droplets and close contact.”

Masks are important to containing asymptomatic spread of COVID-19, when a person is not displaying symptoms, like coughing or sneezing, but is able to spread the virus by talking normally and passing on infected respiratory droplets.

There have been numerous recorded examples of asymptomatic spread of COVID-19, including in Spokane County.

State Health Officer Dr. Kathy Lofy said that masking is incredibly important, especially in the coming weeks and months as regions move into the different phases of Gov. Jay Inslee’s SafeStart plan for reopening the state’s economy.

“I always wear my cloth face covering when I go to the supermarket and other stores because we know people can have the virus in the back of their nose and throat and can spread it even when they’re talking to people in public,” Lofy said on Tuesday.

Lutz hopes wearing masks becomes the new norm, due to the data that suggest how effective it can be in decreasing the spread of disease.

“I sort of rhetorically ask people, ‘Do you want us to open up? Importantly, do you want us to open up and stay open?’ If you do, then I suggest something as simple as a cloth mask, which makes a big difference to ensuring we’re going forward and not backward,” he said.

S-R reporter Adam Shanks contributed to this story.