NFS plague

The NFS plague, or Neurotransmitter Failure Syndrome, was a particularly virulent infection that had engulfed the Border Worlds in the two-thousand years following the Great Catastrophe.

The symptoms of the disease caught its victims by surprise and were very difficult to treat. Sufferers endured a constant buzzing sound in their heads, along with difficulty speaking. Those less-fortunate to survive were described as having their bodies physically fall apart. There was no cure for the disease and only a heavy treatment of antibiotics and other drugs could keep the disease from progressing beyond a certain point. (BFDE: The Healers)

The Daleks had developed a cure for the NFS Plague; a substance called "Variant 7." The drug was a success, freeing the plague victims of years of suffering. However, it was only administered in complex "healing zones" on geo-formed worlds. (BFDE: The Demons)

It was revealed later that the plague itself was engineered by the Daleks as a form of biological and psychological warfare. The plague would weaken the galaxy and the authorities would be desperate for help, no matter who or what it came from. The Daleks would then provide that help, covertly using the plague and their aide as a way to conquer the galaxy. (BFDE: The Warriors, The Future)