On March 12, 2019, our Department of Health Services issued a “Recommendations on Domestic and International Travel” memo. In that memo the DHS specifically recommends that individuals who return to WI from states with “sustained community transmission” should be under self-quarantine for 14- days. Attached is a copy of this memo. Currently those states are California, New York and Washington. Whether or not a state meets this definition is determined by the CDC. If you visit the CDC page link below, scroll down to the map of the US, and hover your mouse over these states, you will see the designation.
https://www.cdc.gov/coronavirus/2019-ncov/cases-in-us.html
Further Information: State of Wisconsin Department of Health Memo