RNA tumor viruses contain ribonucleic acid as their genetic material. The viruses derive their designation from their association with tumors.

RNA tumor viruses are retroviruses that possess the reverse transcriptase enzyme that manufactures deoxyribonucleic acid (DNA) from the RNA template. Indeed, retro is the Latin word for backwards.

The history of RNA tumor viruses extends back to the first decade of the twentieth century. In 1908, it was demonstrated that fluid from a chicken that has leukemia could cause cells to be cancerous, even after the fluid had been filtered to remove all bacteria-sized organisms. Three years later, Peyton Rous identified one such factor, now named the Rous Sarcoma Virus. By the 1950s, many oncogenic viruses had been discovered and the RNA nature of these viruses had been established. In the 1960s, the reverse transcriptase enzyme was discovered. Finally, in 1981, the first human retrovirus was...