Alot of people who are infected with HIV AIDS HEP and so on have partners who are clean of any infections, precautions just need to be taken.
I no somebody who has HIV, unknown at the time she didnt have it and had sex with her partner unprotected several times, it wasnt until she fell pregnant that her bloods came back she was infected.
Baby and partner were fine, their still together and 5 years on after several tests from when they had sex unprotected to this day he never contracted the infection and they had a beautiful baby boy of who also is clear of any infection.