The Department of Public Health Midlands has been notified of a small number of cases of measles at the Midland Regional Hospital, Tullamore.
The cases were confirmed in September but authorities say there is no evidence of further spread in recent weeks.
Local GPs, MIDOC and Hospital Emergency Departments have been informed.
A full investigation is underway and control measures are in place.
The Public Health Department would like to remind the public about the dangers of measles.
People at increased risk are those who are not fully vaccinated with two doses of MMR vaccine or have not had measles in the past.
After being exposed to measles it takes 10 to 12 days for the symptoms to develop and 14 days for the rash to appear.
In the midlands, the uptake rate for the MMR vaccine is 95%.
Measles – three things you need to know:
1. The best protection against measles is to be fully vaccinated with 2 doses of the MMR (Measles-Mumps-Rubella) vaccine.
2. Pregnant women who have not received 2 doses of MMR vaccine and who have been exposed to measles should seek medical advice by phoning their GP or maternity Hospital.
3. If you have any symptoms of measles you should stay at home and not go to crèche, school, college or work. Avoid all visitors. Phone your GP and explain that you may have measles. If you need to see your GP or any other health service call them first before attending - if you don’t you might put other patients at risk.
"Please do not attend the hospital if you think you may have come in contact with a case of measles, seek advice from your GP first if you become unwell," authorities advise.