Olmsted County to require masks in buildings starting Wednesday Olmsted County, and four surrounding counties, classified as seeing "substantial" transmission on virus under federal guidelines, based on new cases. Written By: Randy Petersen | × Masks are worn by many people outside in downtown Rochester Friday morning, May 14, 2021. (Ken Klotzbach / kklotzbach@postbulletin.com) It’s too early to say whether a recent uptick in COVID-19 cases is part of a larger trend. On Sunday, Olmsted County hit 53 confirmed active cases per 100,000 residents, with 84 new cases documented within seven days. “We’re one of the more highly vaccinated counties in the nation,” Olmsted County Public Health Director Graham Briggs said. “We’re not sure exactly how protected that’s going to be against the delta variant.”