The number of confirmed measles cases has risen to nine, up from six last week.
One outbreak of the viral disease is also being reported by the Health Protection Surveillance Centre (HPSC).
As of Monday, 10 further probable or possible measles cases are under investigation: four in HSE Dublin and North East region; four in Dublin and South East; and one each in Dublin and Midlands, and the South West. No cases have been reported in the Mid West, West or North West.
Of the first eight suspected cases reported to the HPSC, all were in people aged 34 years or under, official figures show.
There has been one fatality as a result of measles since the start of the year, when a man in Mullingar, Co Westmeath, died last month having contracted the disease in Birmingham, England.
There are ongoing outbreaks in the UK and across mainland Europe, resulting in a heightened awareness of measles among clinicians in Ireland.
The Health Service Executive has started rolling out a catch-up programme for the MMR (measles, mumps and rubella) vaccine, in response to the rise in measles cases in Europe. Levels of vaccination are below the 95 per cent threshold needed to ensure herd immunity against the disease.
[ Measles Q&A: How do I know if I have measles, and what should I do if I have it?Opens in new window ]
The campaign focuses on delivering the MMR vaccine to more than 300,000 people in key at-risk groups, who may have missed their vaccines in the past, including children, young adults and healthcare workers.
Symptoms of measles vary and include a runny nose, sneezing and a cough, as well as sore red eyes, a temperature of 38 degrees or above and a rash initially in the head and neck area.
The two-dose vaccine for measles is normally given at 12 months and at age four to five, but the HSE has said babies travelling to areas with outbreaks can be vaccinated from six months. However, they still require another vaccine dose over the age of 12 months for continued protection.
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