As I said, that's part of the problem. DND doesn't have the resources to screen everybody, as you suggest, simply because you're talking of tens of thousands of people who would have to be screened medically. It's hard enough to get screened if you are a medical case. There would have to be a significant increase in resources, and that would mean taking resources from other sections within National Defence.
On March 12th, 2015. See this statement in context.