Epidemiologic and laboratory surveillance of the measles outbreak in the Federation of Bosnia and Herzegovina, February 2014-April 2015.

A measles outbreak with two epidemic waves involving 4649 probable and laboratory-confirmed cases was recorded in six out of ten cantons of the Federation of Bosnia and Herzegovina between February 2014 and April 2015. The majority of the patients had never received measles vaccination (3115/4649, 67.00%), and the vaccination status of another 23% was unknown (1066/4649). A total of 281 blood samples were tested serologically. Virus detection was performed using 44 nasopharyngeal swabs. About 57% (161/281) of the laboratory-investigated sera were immunoglobulin M positive, and 95% (42/44) of the swabs were reverse transcriptase-PCR positive. Phylogenetic analysis of sequences obtained from 30 swab samples showed circulation of two variants of genotype D8, but no genotype D4 strains as detected in 2007. Similar involvement of all age groups indicates a problem with vaccine refusal resulting from antivaccination activities in addition to gaps in immunization coverage during the war and postwar period (1992-1998). Differences in ethnicity, vaccine coverage, compliance with review policies of vaccination records and potentially also travel habits may partially explain why only six of ten cantons were affected by the outbreak. The second epidemic wave may in part be due to large-scale migrations due to catastrophic floods in 2014. As a result of the epidemic, 6- to 12-month-old children may now be vaccinated against measles during outbreaks, and public health recommendations for interventions have been strengthened. Additional efforts are required to implement the measures throughout the cantons.