Dr Hildegard Lanstrom was infected and killed by the holo-virus, while Arnold Rimmer narrowly avoided the same fate.
The holo-virus drives the hologram insane, but as an added bonus gives the hologram powerful telekinetic abilities which have the unforeseen side effect of draining and eventually killing the hologram. It is unknown whether the virus was developed like a computer virus or simply came about thanks to random error.
The psychic abilities manifested by those infected with the holo-virus include telepathy, telekinesis and hex vision, an energy weapon that shoots death rays from the hologram's eyes.
The holo-virus has no effect on organics or robots, but they might want to avoid an infectee if they can, as the infected hologram will attempt to attack any other living thing for reasons unknown. As Cat pointed out when they encountered the infected doctor Hildegard Lanstrom, the hex vision is rather erratic ("Why is it we never meet anyone who can shoot straight?") but it is still advisable to keep your distance.
Reasoning with an infected hologram is out of the question as it will either provoke them or they will turn the conversation back on you. Holograms are advised to keep well clear or be isolated by none holographic crew for their own protection as the virus is highly contagious and even speaking with a planet bound infected hologram from a ship is enough to cause infection, as it can be transmitted as radio waves.
Once infected a hologram may not show initial symptoms except for paranoia, as Rimmer locked the rest of the crew in quarantine on Red Dwarf thinking they were carrying infections. After a few days the hologram will have degenerated into complete insanity similar to sociopathy and psychopathy depending on the holograms sane mindset. Telepathic powers will have manifested by then, limiting the lifespan of the hologram depending on how much they use them. By this time the only way to save the hologram from crashing and death is to perform a system restart to purge the virus from the system core. It is advisable afterwards to keep the hologram isolated just to be on the safe side (or a bit of vengeance if you are up to it).