Idahoâs COVID-19 case numbers keep going down, but greater Boise area has hot spots Centers for Disease Control (CDC) Coronavirus Disease 2019 and last updated 2021-04-27 22:43:18-04 Three of the four counties under Central District Healthâs jurisdiction are currently competing for Idahoâs highest seven-day moving average incidence rate for COVID-19 cases reported per 100,000 residents. Elmore County, which includes the city of Mountain Home, owns the highest rate statewide, at 21.8, while Boise County ranks second (16.4) and Ada County third (14.8). Elmore County had a test positivity rate of 9.6% for the week of April 11-17, which was well above the statewide positivity rate of 4.7% for the same week.