My current employer said that they did not like to even offer interviews to anyone who was currently unemployed because there was probably a reason for it and they didn't want people that couldn't keep a job.
In the general case? I am sure (to a certainty sufficiently high to factor into hiring decisions between otherwise equally qualified candidates) that the increase in probability it is non-zero. So yes, I am saying in the general case that people who have been seriously sick before have an elevated chance of being seriously sick again.