Growing proportion of Alberta COVID-19 cases have no known source
Posted: Jul 12, 2021 6:17 PM MT | Last Updated: July 13 This file photo shows Heather Griggs at work as operations chief of the Umatilla County Public Health Department contact tracing centre in Pendleton, Ore. In Alberta, contact tracers have not been able to identify a source of transmission for 39 per cent of active cases.(Ben Lonergan/The Associated Press)