Evolving Retroviruses

Retroviruses, like other RNA (Ribonucleic acid) viruses, evolve at a rate 1 million times that of eukaryotic DNA (Deoxyribonucleic Acid) genomes.

~ Louis M. Mansky (1961 age:56)

What does that mean? HIV (Human Immuno-deficiency Virus) is a million times better at evolving immunity to drugs than bacteria.