The Health Service Executive (HSE) has issued a warning over an increase in meningitis after three people died.
Eleven cases have been reported to the Health Protection Surveillance Centre (HPSC) since the last week in December.
It says three patients diagnosed have died, with the deaths "directly due" to the infection.
Provisional data suggests different strains are circulating and causing disease.
All age groups have been affected - ranging from infants to the elderly.
Of the three patients who died, two different strain types were identified - while none of the patients had contact or links with each other.
— HPSC (@hpscireland) January 9, 2019
Meningitis is a serious illness involving inflammation of the membranes covering the brain and spinal cord.
It can be caused by a variety of different germs, mainly bacterial and viruses.
Bacterial meningitis is less common, but usually more serious than viral meningitis, and requires urgent treatment with antibiotics and may be accompanied by septicaemia (blood poisoning).
Early symptoms can include fever, headache, vomiting, diarrhoea, muscle pain, stomach cramps, fever with cold hands and feet and a rash.
But the HPSC says people should not wait for the rash to appear.
Dr Suzanne Cotter, a specialist in public health medicine at the HPSC, said: "If anyone has any concerns about meningitis they should ring their GP in the first instance.
"Meningitis and septicaemia often happen together and symptoms can appear in any order.
"Some may not appear at all."