However, specialists in public health medicine have warned that the threat of further outbreaks persists if people fail to have themselves immunised against the disease.
Writing in the December issue of Epi-Insight, an online monthly report produced by the Health Protection Surveillance Centre (HPSC), the doctors say the only way to prevent outbreaks is “through measles immunisation, provided by the MMR (measles/mumps/rubella) vaccine”.
“Ireland has made progress to meet the European target for measles elimination (1 case per million) in recent years. But the threat of outbreaks persists as long as there are immunity gaps within the population,” the doctors say.
One case of measles can infect 15-20 unvaccinated people. A vaccine uptake rate of at least 95% with two doses is therefore required to halt endemic transmission of the virus and thus eliminate measles.
The national MMR vaccine update rate in Ireland as of the second quarter of 2016 was 92%, according to HPSC figures, but as low as 89% in Dublin North, Dublin North West and Dublin Central.
Of those infected by the 2016 outbreak, eight were infants, too young to have received the MMR vaccine. Of the remaining 32 eligible for vaccination, 23 (72%) were not vaccinated.
The person behind the outbreak was a passenger on board a flight to Dublin from another European country last April, who was unaware they had measles. Five of the country’s eight public health regions were affected, with the largest number of cases, 27, in the HSE South. While 40 cases were confirmed, another 114 suspected cases were investigated but found not to be measles.
The median age of those affected was eight years. Two cases were health care workers. A total of 19 patients were hospitalised, with a median hospital stay of five days.
The doctors analysing the outbreak said transmission occurred during air travel, in the community and in health care settings, “highlighting the infectivity of measles following unrecognised exposure for most cases”.
They said once cases do occur, “ immediate measures need to be taken to prevent onward transmission among non-immune individuals”.
“These measures include isolation of measles cases either at home or in single rooms in hospitals to prevent spread; vaccination of those not vaccinated (as age appropriate) within 72 hours; or administration of immunoglobulin within six days of exposure for non-immune individuals at high risk of complications.”
The HPSC advises that complications are “quite common, especially in children under the age of five (even more so for children under 1 year), or adults over the age of 20 years”.
They include a severe cough and breathing difficulties (croup), ear infections (1 in 20), viral and bacterial lung infections (pneumonia) (1 in 25), and eye infections (conjunctivitis).
Most of the complications are caused by secondary bacterial infections, which can be treated with antibiotics. More serious problems involving the nervous system are rarer. Severe disease and complications are most likely in infants under 12 months, those with weakened immune systems, and the malnourished.
The last confirmed case in the 2016 outbreak was notified in September and since then, two incubation periods have passed with no further cases identified. Public health medicine specialists say this is “a strong indicator that the ongoing measles transmission from this outbreak has ceased”.