How does KDHE determine which countries or states within the US are part of the list of areas for travel-related quarantine?

For countries outside of the United States, the Kansas Department of Health and Environment (KDHE) refers to the COVID-19 Travel Recommendations by Country which is maintained by the Center for Disease Control (CDC), view COVID-19 Travel Recommendations. Any country with a Level 2 Travel Health Notice or higher has ongoing community transmission and will have a mandatory 14-day quarantine for returning travelers. 

For locations within the United States, KDHE uses a number of sources of data including the number of cases each state has and whether the state is reporting widespread community transmission to make the determination. A formula is used to evaluate new cases in states over a two-week period, then it is adjusted for population size to provide a case rate per 100,000 population. This provides a number that can then be compared to the rate in Kansas. States with significantly higher rates -- approximately 3x higher -- are added to the list

Currently, KDHE does not consider travel within Kansas as a criteria for travel-related quarantine. However, a local health officer may choose to include this as a criteria so you should be aware of your local isolation and quarantine criteria.