This is a retro virus of extreme mutability and capable of being a reservoir virus in the immune cells. This is an RNA virus that uses reverse transcription to hide in the cellular DNA. The viruses genetic material, a single strand of RNA, enters the nucleus of the target cell and with … Read more
Because like most viruses it mutates. Which is why we don't have a cure for other viruses like the common cold or the flu. We can come up for a vaccine one year and then it changes the next.