The Bio-Digital Plague was a devastating disease which struck in in 2435 and nearly wiped humanity out of existence.
The Plague started on earth, during the second human expansion period, and spread out to other worlds. At the time earth had 5 fully developed colonies "Core Worlds" and had just established a dozen more colonies in the "fringe" of human space approximately 100 light-years out. Once the plague started spreading, everything rapidly fell apart. Economies crumbled. Infrastructure fell apart. Governments collapsed. People went crazy with fear, rioting, looting, killing each other in order to survive. In less than a decade, eighty percent of the population of the Earth and the Core Worlds had either died or left.
The plague started as a computer virus that infected the earth's networks. The majority of people on earth interfaced with the networks through the use of cybernetic implants. The virus used these implants to trigger chemical reactions in the brain that would caused a biological virus that would rapidly reconfigure cells and cause them to grow out of control similar to cancer resulting in massive internal and external disfigurement.
The mortality rate of the infected was 90% and the biological component of the virus was contagious itself. The virus rapidly mutated making it incredibly difficult to treat.
The creator of the virus was never discovered.