Can a pathogenic organism be totally resistant to the human immune system? For the purpose of this question, the organism in question must cause a disease.
Examples of organisms that would qualify as totally resistant:
Pathogenic organisms that are completely undetected by the immune system while the disease that they cause runs its course.
Pathogenic organisms that, even if detected, are completely invulnerable the immune system. For instance, macrophages and other immune cells would not be able to destroy even one cell of such an organism.
Is it possible for such a pathogen to exist? Are there any such pathogens? (For the purpose of this question, the HIV and diseases that only manifest in immuno-compromised individuals do not count)