A large number people have been suffering from severe vomiting and diarrhoea in recent days.
The strain of the condition is believed to be the very dangerous 0157 which can be potentially fatal in very extreme cases.
The epicentre of the break-out is believed to be around the Inch area.
However while the source of the bug has not been found, it is not believed the public water supply is connected to the outbreak.
The HSE has confirmed there has been an outbreak of E-Coli but has refused to elaborate on the situation.
It says the Department of Public Health are investigating the outbreak but says that all tests taken so far have ruled out the public water supply as the root of the problem.
One man who suffered form the bug told Donegal Daily that he lost more than one stone in weight as a result.
“I was sick for a week with it solid. I did not eat once and I was constantly in the bathroom.
“I would not wish it on anyone. It was horrific.
“I honestly don’t know how I caught it but I know of three other people who have had it and they suffered like me,” he said.