Ebola is detectable in semen for a year or longer. [0]

So, first, have sex with people you know well enough to know whether they recently recovered from Ebola (pretty rare), and use condoms. Second, I would expect people’s typical “safe sex” practices will keep them ebola-free.

[0] 10% of subjects in this study had ebola in their semen one year after treatment discharge, https://pmc.ncbi.nlm.nih.gov/articles/PMC7875361/