Wow. That is one you don’t get very often. I am old enough to remember outbreaks, but not for over 30 years now, at least in the US> Dr. Salk and the polio vaccine is one of the great examples of the triumph of medical research and public health response against human suffering. It needs to be brought forward more when the anti vaccination people spread PROVEN false data about dangers of vaccines.
But to your question…. I had a client years ago who had had a mild case when young. He was pretty stiff generally, but otherwise had no issues with any of the work we did. But I suspect that, as with any other condition, it will vary. Presumably you have taken a medical history, and asked for guidance from their medical provider. That is good both for liability, and for understanding what is being done in a therapeutic setting, and how you can support that work. You probably also want to be clear about scope of practice…. When I was training I often got people with conditions that required medical help, or physical therapy, and I tried to be clear about my role in supporting, but not duplicating or replacing those treatments.
I also think for some people who had polio when they were young symptoms can recur at some point when they are in middle age. That might be something you would want to look into… not so you can diagnose, but just to be aware.