Going to space appears to be quite the health issue: https://www.theregister.co.uk/2019/01/28/space_weakens_immune_system/
So not only do you get more receptive to every bout of the sniffles floating around, you're also more likely to get cancer, and by the time you arrive at Mars you're quite the nebish.
So not only do you get more receptive to every bout of the sniffles floating around, you're also more likely to get cancer, and by the time you arrive at Mars you're quite the nebish.