SAN MATEO COUNTY – Following new guidance from the California Department of Public Health, officials in San Mateo and Santa Clara Counties are recommending the use of nonmedical masks or other materials to cover their mouth and nose while leaving their home for essential activities to stop the spread of the new coronavirus.

San Mateo County Health and the Santa Clara Department of Public Health both issued statements Thursday advocating for facial covering when leaving the home for essential activities, such as grocery shopping, doctor appointments, exercising, doing laundry and going to the bank. Both counties are under shelter-in-place orders through at least May 3 that restrict residents from leaving their homes for nonessential activities. The state is under stay-at-home orders with nearly identical restrictions on movement until further notice.

Public health experts admonish the public not to use medical N95 masks and surgical masks due to the critical shortage of personal protective equipment front-line medical workers are currently experiencing.

Local officials had previously not recommended the large-scale use of face coverings.

"In addition to shelter-in-place and social distancing requirements, wearing a mask in public is an important tool to stop the community spread of this disease," San Mateo County health officer Scott Morrow said in a statement. "People with no or mild symptoms may have coronavirus and not know it. Wearing face coverings helps protect others from exposure."

Face coverings don't have to be hospital grade to be effective but they need to cover the nose and mouth. Bandanas, fabric masks and neck gaiters are acceptable. Fabric covers and bandanas should be washed frequently with hot water and detergent.

"Wearing a face covering is an additional strategy to reduce the risk of spreading COVID-19. We know that a person can spread the virus before they develop symptoms, or even if they never develop symptoms," Santa Clara County Health Officer and Public Health Director Dr. Sara Cody said in a statement.

"Face coverings are not a substitute for sheltering in place, frequent handwashing, and social distancing, but they do provide an additional layer of prevention when engaging in essential activities." Santa Clara's Public Health Department reported 63 new cases of the new coronavirus Thursday, bringing the countywide total of people who tested positive for COVID-19 to 1,019.