The Infected are an artificial biological being in Lost Contact that latches onto any body part of a sapient being to take control of it, similar to the Flood.
When the Infecter latches onto the target, it starts to disconnect the body from the brain until it reaches the spinal cord. This does not kill the target, instead it disables movement. This means when the host is hurt, the host feels pain, not the Infector. The Infector must be shot for it to feel pain.
An Alpha Infected can tear a sapient being's skull out and over a period of time, connect countless spores to the brain within the skull. After this process, the Alpha Infected reinserts the new skull and seals the wounds with bio-foam, forming an irremovable Infecter.