Beaumont Hospital says that 1,300 people have contacted the helpline set up to deal with the issue of potential CJD infection from surgical instruments.
The Health Service Executive is checking medical records to see how many patients were operated on using instruments that were used on a patient diagnosed with CJD at the hospital.
Creutzfeldt-Jakob disease, a rare brain disease, can be passed on through contaminated surgical instruments.
The infection concern is in the area of neurosurgery at the hospital. The exact number of patients possibly affected has still to be determined.
Beaumont Hospital has confirmed that all planned neurosurgery at the hospital was suspended when concerns over possible CJD infection of surgical instruments emerged. Emergency neurosurgery has continued and planned surgery is due to resume soon.
The HSE said a clinical risk assessment would be conducted for each patient. The review covers the period of 1 June up to 15 July.
The HSE says there is a very low risk of infection, but any patients affected will be monitored to see if they develop any symptoms.
A helpline for concerned patients opened at 8am this morning. The number is 1800-302-602.
1,300 people have already contact the helpline. A spokesperson for the hospital said that most of the callers had been reassured, while others are receiving calls back.
Mewanwhile, Minister for Health James Reilly has said he is very concerned about the developments.
He said there was no clinical suspicion that the patient had CJD and it only emerged during a routine biopsy examination.
Mr Reilly said that once CJD was identified all necessary action was taken.
He said the concerns of patients affected have to be met and he wanted to ensure all protocols are in place.
Speaking on RTÉ's Morning Ireland, Head of Health Protection with the HSE Dr Kevin Kelleher said around ten to 20 people are at risk.
There are a handful of CJD cases in Ireland every year, mainly in people over 50.
It normally causes dementia, a coma and then death within a year.
It is understood the operation on the patient with CJD happened around two weeks before their recent diagnosis.
The instruments were not isolated until after the diagnosis and were used on other patients before then.
If surgical equipment is used on a patient with CJD, international guidelines say it must be put through a highly rigorous sterilisation procedure or destroyed.
Normal sterilisation techniques are not sufficient.
The hospital says it has traced all of the surgical instruments involved in the CJD case.
In a statement last night, the HSE said: "Beaumont Hospital is receiving advice from the Irish Panel on TSE (CJD) and from world experts in the UK, who have dealt with similar cases in the UK and worldwide.
"This group is assessing the circumstances of this case to determine what, if any, risk may exist for other patients."
Beaumont Hospital issued a statement last night saying: "The primary concern of Beaumont Hospital is for its patients and their care.
"Until the necessary risk assessment is completed and the necessary contact made with patients, it is not in a position to discuss the issues under review."
The Irish Patients’ Association has said that at-risk patients need to be contacted as quickly as possible by the HSE and provided with supports.
Speaking on Morning Ireland, IPU spokesperson Stephen McMahon said there is an information deficit and there are many questions that need to be answered, including when did this happen, how many patients have been affected and what is the process of decontamination.