Ongoing large mumps outbreak in the Federation of Bosnia and Herzegovina, Bosnia and Herzegovina, December 2010 to July 2011.

From December 2010 until the end of July 2011, 5,261 mumps cases were recorded in the Federation of Bosnia and Herzegovina, Bosnia and Herzegovina, leading to an incidence of 225.8 per 100,000. Fifteen to 19 year-olds (43%) were most affected and 62% of cases were male. Mumps-specific IgM antibodies were found in about 70% of sera investigated, complications were reported in 41% of 81 hospitalised patients. The outbreak affected mainly those unvaccinated or unaware of their vaccination status and is probably due to vaccination failures during the war and postwar period (1992­1998).