[Environment and occurrence of epidemics].

Mayr, A

Epidemic diseases are defined as the temporary accumulation of dangerous infections diseases in certain areas. They are based on the principles of monocausality of Henle and Koch and represent the most important group of monocausal infectious diseases. Tight ecological relations exist between epidemic diseases and environment. The ecosystem encloses all living organisms as well as the inanimate environment (e.g. soil, water, air, waste). Some chains of infections are demonstrated with American equine encephalitis, rabies, Aujeszky's disease, salmonellosis and so-called soil-born epidemic diseases as examples. Any change of the environment causes enduring effects on the development and progression of epidemic diseases. Many epidemic diseases correlate with certain geographical zones. The variation of climate for instance led to an alteration of the occurrence of epidemic diseases caused by streptococci and staphylococci. A further evidence for the relation of environment and occurrence of epidemic diseases are the seasonal and secular rhythmics in the progress of epidemic diseases. On the basic of new techniques (finger-printing, hybridisation, sequence analysis) the origin of new types of infectious diseases such as American equine encephalitis and infections with Parvo- and Corona viruses can be explained. Finally medicine has to face this thesis: In contrast to the Darwinian theory the recombination of two different infectious agents in a common host may cause evolutionary jumps.