JOHNSTON, Iowa (AP) — The Iowa City school district said Wednesday that 127 students and five staff members tested positive for the coronavirus or are presumed positive, prompting the district to close 11 classrooms and quarantine more than 660 students and 16 staff members due to exposure.

The district was dealing with the infections as Gov. Kim Reynolds maintained Wednesday at a news conference that the virus is not transmitted in schools. Reynolds noted she wasn't familiar with the Iowa City situation.

Speaking generally about infections at schools, Reynolds said, “Most of the teachers and the kids were being exposed outside of the classroom. We weren’t seeing the transmission inside the classroom.”

A school district spokeswoman said over the past few weeks contact tracing for confirmed virus cases in school buildings has revealed an increase in the number of students identified as close contacts to confirmed cases.

“This increase is, in part, due to the influx of students in our buildings since returning to 100% on-site learning and the inability to no longer maintain proper social distancing measures,” said Kristin Pedersen.

She said the contact tracing and quarantine protocols are based on guidance from the Centers for Disease Control and Prevention.

Reynolds has been a strong advocate of classroom learning and has promoted state policies that pushed schools back into classrooms even as some local administrators and school boards resisted.

Federal public health officials voiced increased concern about new coronavirus variants infecting youth as outbreak clusters have been reported among participants in youth sports and in day care centers.

Centers for Disease Control and Prevention Director Rochelle Walensky said Wednesday that some states with high transmission rates should consider suspending youth sports activities to slow the transmission and keep schools open.

Walensky said by the end of March, 80% of all teachers, school staff and childcare workers in the U.S. had received at least one vaccine dose — about 8 million people. She said that level of vaccination helps reach President Joe Biden's goal of broadly opening classrooms safely.

Walensky also said that a coronavirus variant first identified in Europe is now the dominant version of the virus in the country. It is more infectious especially for younger people and can cause more severe illness.

“Across the country were hearing reports of clusters of cases associated with day care centers and youth sports. Hospitals are seeing more and more younger adults — those in their 30s and 40s — admitted with severe disease,” she said.

The trend is reflected in Iowa's results. The state reported 797 new confirmed cases on Wednesday and 13 additional deaths for a total of 5,835 deaths.

Among the positive cases in the last seven days, 25% were among the 18-29 age group and 49% of the positive cases were in people from ages 30-59. Reynolds said 61% of people hospitalized with the virus are now in their 40s, 50s and 60s, a shift from earlier trends in which hospitalized people were older.

In Iowa, 87% of the 65 and older population have had at least one dose of vaccine, she said.

Hospitalizations in Iowa have increased nearly 30% from a month ago to 216. More than 40 virus patients were in intensive care.

Positive cases among those under age 17 were 4% of the total. State data shows more than 41,000 children in Iowa under age 17 have tested positive for the virus in the past year.

Reynolds also announced she would either sign an executive order or work with lawmakers to pass a law to prohibit the practice of requiring proof of vaccination to participate in an event or activity in Iowa. She said she opposes the use of so-called vaccine passports because she believes vaccination is a personal choice and shouldn't be required. The Biden administration has said it has no plans to support such a requirement.