Parents have been urged to have children vaccinated against whooping cough after the confirmation of five cases and an additional eight suspected cases in counties Clare and Limerick.
Children from four-and-a-half months to 17 years have been diagnosed with the disease, according to the Mid-Western Health Board.
It warned that children with whooping cough are "infectious" and should not attend a creche, or summer camp until they have finished a five-day antibiotic course and are well enough to return.
Two of the confirmed cases and six of the suspected cases are in Co Clare and three of the confirmed and two of the suspected cases are in Co Limerick.
Whooping cough, or pertussis, causes long coughing spells, according to a statement issued by the health board. "Children often 'whoop' or vomit after a spasm of coughing.
The infection is most severe in young babies who can become exhausted by the coughing and have difficulty in feeding and breathing. Illness may last several weeks and rarely, in severe cases, can result in brain damage," the health board said.
It said vaccination provided the best protection for children up to seven years and that even if a vaccinated child got the infection, it was likely to be less severe. Pertussis is included in the five-in-one vaccine usually given at two months, four months and six months, available free from GPs, and also the four-in-one booster given at four to six years.