Virus evolution ?

This may be a foolish thought but, viruses may have free reign to evolve and multiply in immunocompromised hosts.


O.K. this virus may have evolved in bats but - people with their immune systems compromised even for a short period of time could they possibly host evolution of a virus?
 
Any condition that allows the virus to grow and replicate, allows for mutation. We have been living with that dynamic since the start. But today, scientist can DESIGN the virus with a warhead, making it a million times more dangerous.