St James's Hospital in Dublin today begins routine testing for HIV and hepatitis B and C for all emergency department patients.
The hospital treats more than 45,000 patients in its emergency department every year and the move follows a pilot project last year, which highlighted the prevalence of the three blood-borne viruses among people attending the ED.
In a statement, the hospital said the testing is in line with international best practice to diagnose new cases and "link disengaged patients back to care".
According to St James's, recent studies show that at least two people per 1,000 in the Dublin area have been diagnosed with HIV.
It says the reported prevalence of hepatitis C in Ireland is between 0.5 and 1.2%, while the numbers of those with hepatitis B is unknown.
The hospital's opt-out pilot screening programme was carried out in March 2014 for patients who were having blood tests taken in the emergency department.
During that pilot phase 10,000 samples were obtained over a 44-week testing period.
Results identified 97 HIV, 44 hepatitis B and 447 hepatitis C cases. Of those identified just over 7% were new HIV cases, 45% were new hepatitis B cases and nearly 13% were new hepatitis C cases.
At the time of the pilot, almost 30% of people already diagnosed with hepatitis C were not receiving care.
Medical Director of the Emergency Department at St James's Hospital Professor Patrick Plunkett said: "It is critically important for those diagnosed with any of these three blood-borne viral infections to receive continual care, some 84% of the previously disengaged patients from the pilot project are now successfully linked back to care."