They have been linked to Acton Scott Historic Working Farm near Craven Arms, which is owned by Shropshire Council.
The farm temporarily closed on June 24 to work with public health partners to take further precautionary measures to reduce risk of visitors catching the infection.
The new measures include providing more visitor handwashing facilities and improving safety information about feeding and touching animals.
Dr Adrian Phillips, consultant with Public Health England West Midlands health protection team, said: “The farm has multiple hand sanitiser points across the site to help protect from coronavirus; however, if people have been touching things which could be infected with E. coli, including touching farm animals, handwashing with warm water and soap is necessary to prevent stomach bugs.
“During spring and summer, especially over holiday periods, there is generally an increase in gastro-intestinal infections which are often associated with a range of activities including farm or park visits, where infections can be picked up by handling or stroking animals. Good hand hygiene for all, and supervised hand hygiene for small children, is essential to minimise the risk of developing a stomach bug.
“E.coli O157 is a relatively rare infection that causes a spectrum of illness ranging from mild through to severe bloody diarrhoea, mostly without fever.
"Sometimes the infection can cause a condition called haemolytic uraemic syndrome (HUS) which affects the kidneys and can be very serious.
"Young children and elderly people are more prone to development of complications associated with E.coli O157.”
Cecilia Motley, Shropshire Council’s cabinet member responsible for leisure, added: “We are using this time to explore the work that is needed to meet the requirements to keep everyone safe.
"Work will include things like more handwashing facilities, extra training for staff and better signage, along with other alterations to how the farm operates.
“Until such time as measures can be put in place the farm will remain closed.”
Anyone who has tickets booked for the attraction will be contacted by the council’s museum service and refunded in full.
Due to the pandemic, all visits to the farm have had to be booked online.