In detect opportunely and prevent you can make a case that the placement of opportunely is intentional and serves to exclude a reading of opportunely detect and prevent where it applies to both nouns.
Detecting a disease when it has already caused symptoms isn't ideal. We'd rather detect it with tests (e.g. genetic), much early, when we might even prevent it from manifesting itself—hence the opportunely.
If you prevent a disease, however, does it matter if you do so opportunely? What does that entail? Preventing it 10 years prior to when it would have manifest itself rather than 5 years?
I read the OP's phrase as opportunely detect so as to prevent.