I have had HIV since 1985. Every few years my personal strain of HIV develops an immunity to the drugs that I am taking, and I have to flip to a new cocktail of 3 or so drugs. The theory is it should be much harder for my personal strain of HIV to simultaneously evolve resistance to three drugs than to one. But they do it! Doctors refer to the drugs as "chemotherapy". The drugs tend to have nasty side effects such as nausea, diarrhea, low energy, neuropathy, nightmares and death (abacavir allergy). So it is quite a trick to find a combination that I can tolerate. The process is not always successful).
Genetic sequencing has greatly improved the process of finding a good combo. Everyone in BC with HIV has had their personal strain of HIV repeatedly genetically sequenced and all its mutations mapped. The mutation map is a nucleotide number followed by a letter for the freak nucleoside. From this map, they know which mutations give resitance to what degree to all the various drugs. So they can tell which drugs will fail even if I have never tried them. There are roughly half a dozen families of drugs. If your personal strain evolves immunity to one drug in a family, it will likely already be resistant (or soon will be resistant) to the others in the family. There must be thousands and thousands of mutations for my strain to fluke out and find a way around almost the entire HIV pharmacopia. (Can anyone enlighten me on the math about the rate of mutation?)
I am in an awkward position in that there is no suitable drug cocktail left. I am awaiting the release of a new drug (doltutegravir) to fill in the third drug of the cocktail. In the meantime I am not taking any drugs, least I aid the HIV to develop immunity to the drugs in an incomplete cocktail.
Danes have been working on an HIV cure, where they trick the HIV to come out of hiding deep in cells. Then it can be completely eradicated by the patient's immune system. I have to hang in there until that works out.
I want to whack creationists over the head with an umbrella when they assure me animals of any sort never evolve. Tell that to my amizingly capable personal strain of HIV evolutionists! I have to admire their computing power, even if they are "trying" to kill me.