Clinical ‘unfamiliarity’ led to delayed measles diagnoses

Delays occurred in the diagnosis of measles during an outbreak in the mid-west last year as many clinicians were no longer familiar with the condition, it has emerged.

A lag-time in notifications of measles meant that some opportunities to implement outbreak control measures were missed, according to a recent Department of Public Health Mid-West newsletter.

The measles outbreak in the region occurred between January and July 2018. Some 42 confirmed or probable cases among 27 males and 15 females were linked to the outbreak, 30 of which occurred in the mid-west.

Twelve cases were aged 0-5 years and the majority (33 cases) were unvaccinated, while the vaccination status of five cases was unknown.

“The most common mode of transmission was within the household, especially in extended families with poor MMR [measles, mumps, and rubella] vaccination uptake. There was also transmission of the infection in the workplace and in healthcare settings.

“Healthcare-associated transmission was an important factor in this outbreak, which emphasises the importance of effective isolation measures in healthcare settings. It is also important that healthcare staff ensure that they are vaccinated against measles.”

Patients who had at least one dose of the MMR vaccine tended to have a milder illness. These patients had atypical presentations with no further onward transmission of measles detected.

The newsletter stated that “as the measles vaccine was introduced in Ireland in 1985, there is a cohort of adults between 30-40 years of age who were never vaccinated and who never had measles (and therefore do not have natural immunity)”.

“However, there were also a number of cases of measles in adults aged over 40 years who would have been assumed to have natural immunity to measles.

“There is an ongoing risk of importation of measles due to a rise in the number of outbreaks across Europe over the past year. The measles outbreak in the mid-west has been linked with a larger outbreak in France.”

To date in 2019, measles outbreaks have occurred in Donegal and North Dublin. In 2018, there were 81 cases of measles notified to the Health Protection Surveillance Centre, compared to 25 in 2017.