Borrelia are bacterial pathogens that infect the cell interior. All organ systems can be affected (multisystem disease). However, Lyme disease rarely occurs alone: other pathogens (co-infections) and additional stresses (e.g. with heavy metals) are frequent accompanying factors. The symptoms are correspondingly varied. The number and severity of symptoms vary greatly from person to person. In the course of time, the symptoms change when the inflammations, immune phenomena and secondary disorders caused by the pathogens develop a potentiating momentum of their own. Often, it is no longer possible to distinguish between directly pathogen-related symptoms and indirect secondary symptoms.