Given sustained high vaccination coverage and enhanced surveillance for measles, Spain has been free of endemic measles transmission since 2014, achieving elimination certification from the World Health Organization in 2017. In November 2017, measles was introduced through an imported case travelling to the Valencian Community, causing an interregional outbreak. Here, we describe the outbreak using data reported to the national epidemiological surveillance network. The outbreak involved 154 cases (67 males, 87 females) notified in four regions; 148 were laboratory-confirmed and six epidemiologically linked. Most cases were adults aged 30-39 (n = 62, 40.3%) years. Sixty-two cases were hospitalised (40.3%) and 35 presented complications (22.7%). Two thirds of the cases (n = 102) were unvaccinated including 11 infants (≤ 1 year) not yet eligible for vaccination. The main route of transmission was nosocomial; at least six healthcare facilities and 41 healthcare workers and support personnel were affected. Sequencing of the viral nucleoprotein C-terminus (N450) identified genotype B3, belonging to the circulating MVs/Dublin.IRL/8.16-variant. Control measures were implemented, and the outbreak was contained in July 2018. The outbreak highlighted that raising awareness about measles and improving the vaccination coverage in under-vaccinated subgroups and personnel of healthcare facilities are key measures for prevention of future outbreaks.
Keywords: Healthcare workers; Outbreak; Spain; Waning immunity; measles; nosocomial transmission.