Andromeda was a deadly disease of unknown alien origin. It infected a village and wiped out near all the residents, save for a newborn baby and a drunken old man. It was nearly eradicated and stored away. However it was accidentally re-released into a rural mountain village where it infected and killed all the residents. An unknown country and the Hyakki Empire went after it with the Getter Team tailing them. Ryoma Nagare blamed the Hyakki Empire for what happened, General Hidler however tells Ryoma that the disease was released by humans and that the empire was just there to claim it. Ryoma refused to believe their claims and smashed their ship the Jeronigan in anger. The claims were later confirmed by Dr. Satome, saying that it was Japan's own government that did so.
The name for Andromeda likely comes from The Andromeda Strain a science fiction film from 1971.