The positivity rate of coronavirus tests will be the primary factor in deciding whether Iowa schools will hold in-person classes full or part time, or whether schools will temporarily switch to online learning, Gov. Kim Reynolds announced Thursday.
Reynolds said the metric will be a two-week average of positivity rates for the counties in which school districts operate.
Positivity rates are determined by comparing the number of confirmed coronavirus cases over a certain period of time with the number of tests that were evaluated.
Carroll County, for instance, currently has a 14-day positivity rate of about 5.8 percent, based on a Times Herald analysis of data published on the state's coronavirus website that shows 40 confirmed cases out of 687 total tests.
Local county health and emergency management officials said Thursday that the state hasn't been supplying them with that rate on an ongoing basis.
"It sounds like it should be on the website in a couple of days," said Nicole Schwering, public health director for Carroll County.
The county's current rate puts it in the "minimal to moderate" community transmission category, based on new state standards, which means on-site school learning would be required with some exceptions for individual students.
School districts may request to switch to online learning for an entire school building or the whole district only if:
— The positivity rate is between 15 and 20 percent and 10 percent of students are absent from school.
— The positivity rate exceeds 20 percent.
To put those rates in perspective, here were the 14-day rates in three western Iowa counties when food-processing facility outbreaks caused their confirmed coronavirus cases to surge:
— Crawford County: 20.9 percent. That was from May 13 to 26, when there were 285 new cases.
— Woodbury County: 22 percent. That was from May 4 to 17, when there were 1,040 new cases.
— Buena Vista County: 29 percent. That was from May 26 to June 8, when there were 1,070 cases.
Crawford's current 14-day rate is about 7.1 percent, based on the state's available data.
The accuracy of that data is unclear, because the state's website has been inconsistent and difficult to interpret. For instance, the site shows two different positivity rates for Woodbury County for Thursday — 9.8 percent and 10.3 percent — as well as conflicting numbers of tests and confirmed cases for that day, and all of that information resides on the same webpage.
The World Health Organization has said that community spread of the virus is considered under control when the average positivity rate is less than 5 percent. The U.S. Surgeon General said last week that generally it's best to have less than a 10-percent positivity rate.
Reynolds emphasized the importance of in-person learning when she spoke Thursday about the new guidelines. She said schools nurture social and emotional skills in addition to academics and provide a safe space for student when their parents are at work.
"We need to keep our next generation learning, growing and preparing for a bright future," she said.
Reynolds downplayed the threat of coronavirus transmission in schools and said, "Children are less likely to contract and spread the virus."
Some studies back that idea, but Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said this week that children older than 9 can spread the virus as well as adults.
Reynolds, who wore a face mask when she walked to a podium before she spoke Thursday, said the state would not mandate masks for students but left open the option for districts to require them.
She reiterated advice that she has given for months: "If you can't social distance, wear a mask."
Most classrooms do not have enough room to ensure 6 feet of space — the standard for social distancing — between students.