[Update in infectious diseases. Part I: epidemiology].

A number of infectious agents has been newly detected in the last 10 years. Climatic changes and migration have been the most important factors in the emergence of new and old infections. Additionally, new methods for the detection of DNA and RNA have played an important role in the detection of agents difficult to culture. Relevant new bacterial pathogens are Bartonella henselae (cat scratch disease, bacillary angiomatosis), Tropheryma whippeli (Whipple's disease) and new Rickettsiae. Newly detected viral pathogens include Sin-nombre virus (pulmonary Hanta virus syndrome), Nipah- and Hendra virus and avian influenza. Bovine spongiform encephalopathy has been transmitted to humans causing the newly described syndrome of variant Creuzfeldt-Jakob disease. The extent of this new epidemic is not yet clear. These trends from the last years clearly indicate, that further new infections and infectious agents will be detected in the future.