Good bacteria and good fungus can work together in cooperating communities to promote health.  Prior exposure to many viruses provide immunity to re-infection.  Immortal bacteria, fungus, parasites, and persistent viral infection can work synergistically to damage health.  Immortal intracellular pathogens can spread silently over time; and combine with fungus, viruses, and parasites to hide from and defeat the immune system. Over time, the increased infectious burden and the toxic mix of pathogens can erupt or be triggered to become chronic disease.