PORTLAND, Ore. (AP) — Health officials in Oregon’s most populous county said Monday they strongly recommend that people wear masks in all indoor public spaces regardless of vaccine status.

Multnomah County officials said in news release that the advisory was issued in response to COVID-19 cases increasing largely because of the highly-contagious delta variant. Portland is in Multnomah County.

Public Health Director Jessica Guernsey said if people don’t act, we can expect an exponential rise in cases, especially in pockets with low vaccinations.

“This could lead to preventable hospitalizations and even death,” Guernsey said in the news release. “Masking is a step we can all take right now to keep businesses open and move ahead with our plans for the school year.”

County health officials are particularly worried about the delta variant, which is roughly twice as contagious as earlier virus strains and may cause more severe illness. Eight counties in Western Washington are also recommending people wear masks in public indoor settings as are officials in Los Angeles County and San Francisco Bay Area counties.

“Vaccination remains the very best protection against this virus and its variants, so for anyone who can, don’t wait. Get your shot,” Guernsey said. “But we need a quick course correction to protect children and other people right now. And masks offer that protection.”