For TB in particular, we have well-established ways of treating people so they are no longer infectious, which is of benefit to them and to preventing further spread. That's true for most of the conditions. For some of them it's a question of isolating the person, and there are other preventive measures that can be taken.
One of the problems is the assumption that if there's a certain amount of screening before the person arrives—and I'm not taking away from that process—it covers everything. But in some provinces, including my own, when an immigrant arrives they don't even have access to health care. So the system may potentially put people at more risk, because there isn't an easy way that somebody can be taken in and checked out fully.
I see it in the same way that everyone has an annual health check. It's the idea that somebody in primary care reviews the health of the new arrival.
I also want to reiterate that immigrants who arrive in Canada are healthier than Canadians.