Passengers on board a bus travelling from Dublin Airport to County Tipperary may have been exposed to measles.
The alert affects a JJ Kavanagh bus - number 717 - which departed Dublin Airport for Clonmel at 4pm on Saturday afternoon.
It also affects Aer Lingus flight EI-451, which left Naples for Dublin at 11.40am on Saturday morning.
The HSE said any passenger who is pregnant, immuno-compromised or under 12-months-old should contact a GP or hospital for immediate advice.
Other passengers should be alert for any symptoms such as a cough, sore eyes, high temperature or a rash until Friday September 6th.
Passengers are advised to ring ahead before attending any healthcare setting to let them know you were exposed - and not to make any further travel arrangements.
Earlier this year, a person died in Ireland after contracting measles.
Main image: A person with measles. Picture by: Alamy.com