Mutation...

Mutation has long been the BFF of many viruses, especially HIV.  These mutations have allowed viral culprits to plague mankind.   Even as a vaccines or remedies are developed, the viruses are busy breeding the next gen version of themselves to better withstand these assaults.

HIV & it mutations have allowed it to certain level of immunity towards standard meds.  It has proven capable of altering its makeup to adapt to specifically designed, HIV meds.  Drug resistance has been & will remain a serious issue when dealing with HIV.  

Overtime many species; rats, roaches, even humans, can become resistant to things.    The problem for these species is the amount of time it takes for them to produce the next generation.  Viruses are in a near constant state of self replication.  Compared to humans that's amazing.  By the time a child is born, grows & is capable of procreation, a virus could well be into generations marked by the 1,000's , if not more.

Mutations aren't always for the better. & according to this article researchers have a mutation that limits HIV's ability to be resistant to medications.  This could prove to be 1 the biggest discoveries in dealing with this illness.  This, along with other treatments, might actually allow the possibility of a vaccine or cure.  This should prove interesting.

Cya...