Chronic inflammatory bacterial infections are rare, are difficult to detect, and can be associated with severe diseases including cancer. Therapeutic and prophylactic measures are not easy to implement against these infectious diseases, since their traits include various activities to evading and manipulating the immune system of the host organism. One paradigm and model organism for chronic inflammatory disease is the bacterial agent of severe human stomach pathologies, Helicobacter pylori. H. pylori is predominantly acquired in early childhood within families and, even at an early age, can be linked to serious symptoms such as anemia, growth retardation, and perforating gastric ulcers. With increasing age, the incidence of gastric and duodenal ulcers rises in infected persons, and the infection can also promote various malignancies of the stomach. With a global view on public health, the infection is one of the most prevalent, since about 50% of the world population carries the bacteria. Every single infected individual has their own individually adapted H. pylori strain, since the bacteria can quickly diversify and adapt upon transmission. A spontaneous clearance of the infection has been observed quite rarely. Simple therapeutic options are not available yet, nor is a prophylactic vaccine. Closely related bacteria exist in humans and various animals, where they can cause chronic infections and inflammation in the gastrointestinal tract. The biology of these infectious agents is therefore of broad interest for understanding chronic bacterial infections and devising new ways to antagonize them.