As the BA.5 omicron subvariant fuels a rise in COVID-19 cases and hospitalizations rise in many areas around the country, some school districts are bringing back mask mandates.

Indoor masking rules have been largely abandoned since the earlier days of the pandemic, when vaccines were not yet available. But with high community spread in many counties and the fall semester looming, some administrators are reconsidering their position.

Gwinnett County, Georgia, started requiring all employees to wear masks again last week and is strongly encouraging kids and visitors to mask up, too. Covering the states largest school district, located outside of Atlanta, the order affects some 120 school buildings. A neighboring district, in Clayton County, similarly announced a mask requirement for employees and visitors.

Also last week, Kentuckys largest school system, located in Jefferson County, started requiring masks for everyone in school buildings and on buses.

San Diego County announced the return of the mandate, as well, at least for the next few weeks.

COVID-19 transmission is classified as high in all four counties, according to the Centers for Disease Control and Prevention. The agency says three-quarters of U.S. counties are experiencing medium or high community spread at the moment.

Los Angeles County is mulling a new universal indoor mask mandate countywide, although officials may put it off considering the latest data shows signs of a decline in spread; a decision is expected this week.

Omicron BA.5 is currently the dominant variant spreading around the U.S., the CDC says, noting that the strain may be more contagious than past omicron variants. Future coronavirus booster shots may be calibrated to target the BA.5 and BA.4 variants specifically, but available vaccines still offer very strong protections against severe illness and death from the virus.