We have evolved with other animals. Viruses have evolved to use us as their reproductive mechanism. Thus they target us. More specifically they target specific parts of us eg the SARS-CoV-2 coronavirus targets the respiratory system. Viruses are simple. A protein coat outer shell plus inner DNA / RNA. Can we (Have we done it already?) use viruses as drug delivery mechanisms? Put DNA / RNA / drug molecules inside the virus protein coat. The virus is setup (for lack of better terminology - though years/decades/millennia of evolution) to target a specific part of our body.