Mumps resurgence in Denmark.

Background: The past decade has witnessed a resurgence of parotitisvirus (mumps) in several countries where seemingly good mumps control otherwise had been achieved through vaccination. Recently detection of mumps has increased in Denmark.

Objectives: To describe the age-specific changes and time trends of parotitisvirus detection in Denmark over a 10 year period.

Study Design: Retrospective cohort study based on national laboratory data for parotitisvirus typing surveillance and national epidemiology data for mumps reporting.

Results: The parotitisvirus detection rate has increased almost 10 times during the past 10 years from an incidence <0.1 per 100,000 in 2003 to 0.96 per 100,000 in 2013. The age distribution has shifted from children to young adults, and most cases are unvaccinated (54%) or vaccinated once (41%). The increase is due mainly to the existence of cohorts with low MMR vaccine coverage.

Conclusion: Analysis of mumps surveillance data from Denmark documents that the incidence of mumps is increasing, and that the resurgence of parotitisvirus is primarily occurring among young Danish adults. Almost half of the infected clinical mumps cases had received the first dose of MMR.