They will find out so there is no point in hiding it. Not sure your whole case but spousal sponsorship does not include a medical inadmissibility clause. HIV positive people can immigrate to Canada as long as their care does not cost over the indicated limits. Each case is different but HIV positive applicants have immigrated. You should be aware that Canada doesn't have a national pharmacare program. You will have to look for employment that offers drug coverage. Not all jobs do.