Thousands of bacteria, viruses and parasites exist in the world. Some of the bacteria are part of our body and aid in bodily functions. Some are pathogens that cause acute disease and resolve, leaving behind greater immunity. A few of these bacterial and viral pathogens are immortal, and once acquired continue to spread silently in the body. The immortal pathogens can cause a serious acute infection, and after the acute infection resolves the immortal pathogens can evolve and combine with other pathogens over years and decades to become a chronic disease.