Up to 5,000 patients are to be informed that they have been exposed to a dangerous superbug.
CPE is an antibiotic-resistant bacteria which is harmless when in the gut, but is fatal in up to 50% of cases when it gets into a person's bloodstream.
The HSE is making plans to contact in-patients who came into contact with people who had CPE during their hospital stay.
Stephen McMahon of the Irish Patients' Association says it is very difficult to treat.
"This is a superbug because it is very difficult to find an antibiotic that will actually kill it off and it creates other problems in the health system as well as having a huge mortality impact on patient's lives," said Mr McMahon.
"But also, when the hospital tries to decontaminate it, you can't simply carry out the contaminated items through the hospitals."
Mr McMahon says there are questions to answer over how the HSE and its expert group are dealing with the issue.
"There's also the issue too that the meetings were supposed to be held every fortnight or weekly but we find that on June 14 they say that the next meeting was to be on June 28 and this hasn't been held and we need to know why this is considering the sheer importance of having this national campaign to deal with the issue."