The natural reservoir of EHEC is the intestinal tract of various ruminants such as cattle, goats, deers, which do not suffer from EHEC infections but can shed the organism over a long time.
The following three transmission routes of EHEC to humans are considered to be valid:
1. Transmission via contaminated food or drinking water
In the USA, minced meet was identified as the most common contaminated food. In addition, contaminated appel juice, radish, sproats and other food were responsible for EHEC infections. Moreover, some infections were associated with the consumption of water.
2. Transmission from human to human
This transmission route occurs mainly within groups of risk persons such as within kindergardens or nursing homes. Especially the acid tollerance of EHEC together with the low infection dose (below 100 bacterial cells) faciliates the transmission via direct or indirect contact between humans.
3. Contact with animals
Contact with animals (ruminants) during work-related processing of food can lead to an EHEC infection. Until today, the impact of petting zoos, which are frequently visited by children and where known EHEC reservoirs are present (goats, sheeps), is unknown.