[A majority of the US population carries the non-genital herpes virus, mostly contracted in childhood. It is usually dormant but a weakened immune system can allow it to flare up.]
Decades ago, science fiction novels used to talk about terraforming and fuel issues as the principal challenges to space travel and the settlement of other planets. It’s looking like there are even more fundamental issues that need to be addressed before we can get going. It’s not like the best doctors will be available to treat astronauts going where no man has gone before.