In the sci-fi TV series Doctor Who, nanogenes are a type of sub-atomic robot created by an unseen race called the Chula. They swarm throughout the enclosed environments of Chula starships and can repair any wound or injury. They appear in the 2005 episodes The Empty Child and The Doctor Dances.
In 1942 at the height of the Second World War, a Chula medical capsule was plunged down to Earth where it crashed in a blitzed London. Captain Jack Harkness, a former Time Agent from the 51st century turned con artist, had used the capsule in a plot to rip off the Time Agency, claiming that he had something of value to trade when in reality he was trading junk. He had hoped to make the deal and leave Earth with his money before the buyer could see his merchandise, which was due to be destroyed by a German bomb during an air raid. What Harkness was unaware of was that the medical capsule contained nanogenes, which escaped the capsule when it ruptured on impact. They discovered the body of a child who had been killed by the capsule's impact and tried to revive him. However, the nanogenes had never encountered a human before and the boy was covered with wounds and was wearing a gas mask. The boy was revived, but his injuries remained and his mask had been fused to his face, since that's what the nanogenes thought humans were supposed to look like. The boy's mind was fractured and he went wandering through London searching for his mother, not even recognizing who his mother was or anyone else. With every person he touched, the empty child passed on the self-replicating nanogenes which transformed their victims into mindless, gas-masked zombies. Fortunately, the Doctor, Rose Tyler and Captain Jack were able to find Nancy, a teenage girl who turned out to be the boy's mother. When Nancy made contact with her son Jamie, the nanogenes recognized that their DNA was the same and realised their error. The swarm then passed on to the other transformed humans and returned them to normal. The nanogenes then went dormant and the Doctor set the Chula capsule to self-destruct, making sure that there would be no evidence that the capsule had ever been there.