The Health Service Executive has notified the Louth Country Coroner of the deaths of four patients at Our Lady of Lourdes Hospital, Drogheda.
It is believed that the bacterial infection, Clostridium Difficile, may have been a factor in their deaths.
There are now 13 confirmed cases of C Diff in the hospital, with another 20 patients showing signs of infection.
The hospital says 70 beds are closed due to the outbreak.
Following talks with Louth County Coroner Ronan Maguire, the hospital agreed to inform him of all deaths in Our Lady of Lourdes during the escalation phase of the outbreak.
Only an inquest will be able to say if C Diff was a factor in the patients' deaths.
Restrictions at Our Lady of Lourdes are still in place, with many patients being sent to other hospitals in the region and in Dublin.
All non-emergency procedures have been cancelled, although out-patient clinics are proceeding as normal.
There are also restrictions in place for visitors to the hospital.