The disease is highly contagious.
An outbreak of measles has been reported in Westmeath.
HSE Midlands says it's been notified of four cases, and full investigative and outbreak control measures have been put in place.
It's warning people of the symptoms of the disease - which is highly contagious and can become serious.
Anyone who has not received two doses of the MMR vaccine is advised to contact their GP.
Dr. Douglas Hamilton, consultant in public health medicine in the midlands, outlines symptoms to look out for: