Where has this strain come from?
Germany, specifically the north, is the geographical source. The source appears to be contaminated salad vegetables. Initially scientists thought cucumbers were the source of infection, however, this has not been confirmed. Other foods are now being investigated.
How could salad vegetables become infected with a gut bacteria?
Fertiliser could be the prime source of infection, while irrigation water from streams contaminated with faeces from infected animals could also be to blame. Cattle, for instance, can carry E.coli in their guts without becoming il