Ada, Kootenai counties make up bulk of Idahoâs latest COVID-19 cases Centers for Disease Control and Prevention (CDC) COVID-19 and last updated 2020-12-24 22:31:04-05 Ada and Kootenai counties accounted for more than half of Idahoâs new confirmed cases of COVID-19 on Thursday. The Gem State reported 855 new confirmed cases and 312 new probable cases for a total 1,167 cases, according to state and public health district data. The Idaho Department of Health and Welfare added 349 new cases of COVID-19 to Ada Countyâs tally, bringing the countyâs total to 31,485 overall. However, the countyâs true caseload is still unclear as Boise-based Central District Health works through a significant backlog of cases. CDH estimates the 14-day average incidence rate in Ada dropped from 85 to 67 cases per 100,000 residents last week.