The Health Service Executive has said it is investigating four cases of meningococcal meningitis.
The cases were reported in the last week of September. Three of the cases have been confirmed and one remains as a "possible" infection.
Three of the cases involve young adults and one case involves a child less than 10 years of age.
The HSE said that two of the individuals affected have died.
There is no known link between the cases, as they were reported in different regions of the country.
In a statement today, the HSE said that any close contacts of the affected individuals will be treated with antibiotics to prevent infection and "will also be offered vaccine if appropriate".
The HSE said meningitis is a serious illness that can be caused by a variety of different germs, "mainly bacterial and viruses".
"Bacterial meningitis may be accompanied by septicaemia (blood poisoning). The bacteria live naturally in the nose and throat of normal healthy persons without causing illness. The spread of the bacteria is caused by droplets from the nose and mouth. The illness occurs most frequently in young children and adolescents, usually as isolated cases. Bacterial meningitis or septicaemia requires urgent antibiotic treatment," it said.
The HSE urged anyone showing early symptoms such as; fever, headache, neck stiffness, vomiting, drowsiness, stomach cramps or fever with cold hands and feet, to seek medical assistance.
It added that if someone is ill and getting worse, they should "get medical help immediately".