I haven’t seen any posts about this yet. Ohio Gov Mike DeWine (R) retweeted Dr. Amy Acton, Director of Ohio Dept of Health (ODH) asserting this based upon the dozens of suspected coronavirus cases discovered recently: "We know now, just the fact of community spread says that at least 1%, at the very least 1% of our population is carrying this virus in Ohio today." Cleveland channel 5 has a story up. Presumably this estimate was arrived at mathematically by epidemiologists examining the prevalence of new cases around the state.
This report also mentions that all schools in Ohio are being closed from Monday.
(Updated) There was a lot of skepticism so I am attaching a screenshot of Mike DeWine’s twitter post. He is pretty right-wing so it is interesting he is not trying to minimize the situation.