The HSE says the number of measles cases in an outbreak in Dublin has risen to 11.
It says it is particularly concerned about children who attended Temple Street Children's Hospital in Dublin recently.
It follows the discovery of five more cases of the infectious disease.
Doctors are advising parents to be on the alert for symptoms if their child was in Temple Street on July 25th, 26th or 27th, or on August 6th.
Measles symptoms include:
The HSE says measles can be a serious illness and is highly infectious.
It says the risk of getting the disease lasts up to 21 days after contact.