The Health Service Executive (HSE) has issued a warning over an increase in meningococcal disease after three people died.
It is advising the public to be vigilant regarding meningococcal meningitis/septicaemia, as there has been a "noted increase" in meningococcal disease in the last two weeks.
Eleven cases have been notified to the Health Protection Surveillance Centre (HPSC) since the last week in December.
It says three patients diagnosed with meningococcal disease have died, with the deaths "directly due" to the infection.
Provisional data on the strain types indicates that 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 were identified as having had contact or links with each other.
What is meningitis?
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 is usually more serious than viral meningitis, and requires urgent treatment with antibiotics and may be accompanied by septicaemia (blood poisoning).
The bacteria live naturally in the nose and throat of normal healthy persons without causing illness and the spread of the bacteria is caused by droplets from the nose and mouth.
The 11 cases compares to five cases for the same time period last year.
In 2018, a total of 89 meningococcal cases were notified compared to 76 in 2017.
Dr Suzanne Cotter is a specialist in public health medicine at the HPSC: "Although meningococcal disease incidence generally increases in the winter months, the recent increase is cause for concern and the HSE wishes to alert the public to the signs and symptoms of this disease so that immediate medical attention can be sought if someone has symptoms that could be caused by this bug.
"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."
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 Cotter adds: "Parents of children should also check that they are up-to-date regarding their childhood meningococcal vaccinations."