Measles outbreak in 2019: a warning for the post-COVID-19 pandemic period.

Introduction. At the end of 2019 and the year before, there was a significant spread of measles in the World Health Organization (WHO) European Region. Gap statement. Among the countries that reported, a measles outbreak was Bosnia and Herzegovina (BiH). Aim. To describe the measles outbreak in BiH (an entity of the Federation of BiH, FBiH) in 2019. Methodology. Confirmatory IgM serology, measles nucleic acid detection by real-time RT-PCR and virus genotyping were done in the WHO-accredited laboratory for measles and rubella at the Clinical Center of the University of Sarajevo, Unit for Clinical Microbiology. Genotype was determined in all measles-RNA-positive cases by sequence analysis of the 450 nt fragment coding the C-terminal of measles virus nucleoprotein (N). Results. From 1 January to 31 December 2019, 1332 measles cases were reported, with the peak observed in April 2019 (413/1332, 31.01 %). Sarajevo Canton had the highest incidence, number of cases and percentage (206.4; 868/1332; 65.17 %) of measles cases. Around four-fifths of infected persons were unvaccinated (1086/1332, 81.53 %), while 4.58 % of the patients (61/1332) were immunized with one dose of measles-containing vaccine. The highest proportion of cases was found in children 0-6 years of age (738/1332, 55.41 %). Measles IgM positivity was determined in 75.88 % (346/456), while virus RNA was detected in 82.46 % (47/57) of the swab samples. All measles virus sequences belonged to genotype B3. SNP (position 216: C=>T) was detected in 1 of the 40 sequences obtained during this outbreak. Conclusion. Due to suboptimal immunization coverage, BiH belongs to countries at a high risk for measles outbreaks. Post-COVID-19 (coronavirus disease 2019) pandemic, targeted and tailored strategies are required to ensure routine vaccination demand and acceptance and broad partner and stakeholder group participation.