In the week ending June 15, new cases of COVID-19 in Multnomah County nearly doubled from the previous week. That's part of an upswing in cases in the county, state and a significant portion of states across the country.

Portland had been preparing to open June 12, but with hours to go before reaching that promised land, Gov. Kate Brown slammed the door—rejecting the county's application for at least a week. It's unclear if the county will reopen this week after the governor chose to impose the one-week pause statewide.

Where are all these cases coming from? The short answer is that public health officials don't know, for a lot of the cases.

Roughly 40 percent of cases haven't been traced to a previous infection since the beginning of May. The percentage of cases with no defined source—termed "community spread"—has not declined.

That means that the county is far from being able to identify all the places where disease is currently and block the further spread of the disease.