Once acquired, immortal pathogens can spread in the body through migration to adjacent tissue; erosion through tissue; or through metastasis in the lymphatics, blood stream, muscle tissue, and nervous system.  Immortal pathogens can spread to the eyes, nose, or mouth, through self-inoculation; and some immortal pathogens can cross the placenta, to infect a fetus.

Immortal pathogens cause the same type of tissue damage, organ damage, and chronic diseases, in animals and humans. Different immortal pathogen may attack similarly or differently from other immortal pathogens.  Immortal pathogens which cross the placenta attack and damage the same type of tissue and organs in the fetus, as the pathogens attack and damage in animals and humans.