Bay Area counties will announce a new order on Friday that will require residents to wear masks and face coverings while in public, Marin County’s health officer said Thursday in a video statement.

The new requirement will go into effect at noon on Wednesday to give time to the public to prepare, Dr. Matt Willis, the health officer, said in a YouTube video. Willis did not say which of the Bay Area counties were joining to put out the order.

He said several Bay Area county public health officers have been considering what to do after the May 3 expiration of the existing shelter-at-home order. He said the options were: extending the order with no changes, lifting the order completely, or extending the order but with limited modifications to allow some loosening of restrictions.

“The regional public health officers who authored the first shelter in place order have decided to go with that third option, a careful and sequential alteration of the shelter in place order,” Willis said.

The specific details of this potential order remain to be seen. Willis, who had been diagnosed with COVID-19 and has recovered, said the specific language of the new, amplified order will be released on Friday.

Willis said a crucial part of the Bay Area’s “new normal” will mean everyone wearing a face covering when in situations where there could be transmission, such as in public and when in close quarters with people who are not in one’s household. Children under the age of 6 will be exempt, he said.

“We don’t need to wear it when we are alone in doors, with those we live with, or out by ourselves on a walk,” Willis said. “If this just feels like another order, it’s important to realize that this actually enables us to lift other more restrictive orders.”

As public health officials are learning more about the spread of the coronavirus — such as how asymptomatic people can still be infectious to others — Willis said simply covering one’s face with a cloth mask or other homemade covering is an effective way to reduce transmission of droplets into the environment.

Willis said the order will not require residents to use medical-grade masks or N95 masks, which are needed for the region’s health care workers and first responders.

“Covering our faces is something that we do to protect all of us. The decision to cover your face is the decision to support our well being as a community,” Willis said. “If we can really do this, if we can get this down, it will help eventually give us more freedom to travel and interact more within our community. Facial covering will be an important part of our new normal.”

Willis said the Bay Area’s shelter-in-place efforts over the past month have proven that residents are powerful when working together to slow the spread of the coronavirus, and urged residents to maintain that “same spirit” moving forward.

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In the final seconds of the YouTube announcement, Willis pulled a cloth mask over his nose and mouth, looked into the camera, and said, “So thank you Marin, cover your face, and stay healthy.”

Marin County’s announcement comes the same day as Sonoma County public health officials announced staff and visitors of patient care facilities are required to wear medical-grade isolation or surgical masks. Some staff may be allowed to wear a fabric or cloth face covering to preserve medical-grade supplies. The order also requires first responders to wear medical-grade masks anytime they interact with the public or patients.

Earlier this week, Sonoma County public health officials announced an order of their own requiring residents to wear facial coverings in public starting Friday to guard against spread of the coronavirus.

The Sonoma order does not apply when a person is driving alone, unless they roll down the vehicle windows to speak with non-household members. Residents are not also required to wear a face covering when going for a run or walk in the neighborhood, but officials encouraged residents to bring a mask in the event they encounter other people.

Lauren Hernandez is a San Francisco Chronicle staff writer. Email: lauren.hernandez@sfchronicle.com Twitter: @ByLHernandez