However, beginning in July 2009, the largest U.S. mumps outbreak since 2006 has occurred, with 179 confirmed or probable cases reported in multiple locations in two states and an additional 15 cases reported in Canada as of October 30.

The index case was an 11-year-old boy who had returned on June 17 from the United Kingdom where an ongoing mumps outbreak involves more than 4000 cases. Because of the potential for more extensive disease transmission, efforts should be made to heighten surveillance for mumps and assure that children and adults are appropriately vaccinated against this disease.