DNA and RNA: Viruses

Viruses have been with us since the very beginning of life; probably from when we first arose as a species (they would have been evolving right along with us). These formidable agents of infection don't survive in the fossil record but evidence from ancient civilisations reveals some of the long history we've reluctantly shared with them.
Egyptian drawings dating back to around 1400BC depict people with the wasted legs characteristic of poliomyelitis, or polio, a viral disease that often causes paralysis of the limbs. Smallpox causes scars that can still be seen on the mummy of Ramses 5th, who died in 1157BC.
Some 3000 years later, in the 1790s, English country doctor Edward Jenner developed the worlds first reliable vaccine against smallpox when he noticed that people who contracted the minor ailment of cowpox were immune to the much more serious disease of smallpox. Jenner deliberately began infecting people with cowpox to fight smallpox. The human fight to stop viral infection through the application of science had begun.
Jenner did not actually know that he was fighting a virus, the word wasn't even in use then. …