रित्रभाइरासफोरा बिसोर भाइरासनि गोदान फोलेराव गोख्रैयै बास्लायनो ( सोलायनो ) हायो हिसाबै सोलिनो जुजिगासिनो दं ।
Retroviruses are challenging to treat as they can rapidly alter mutate into new strains of virus .