Objectives: Due to high vaccine coverage in Niigata, we had no outbreaks of measles from 1997 to 2003 but an opportunity to study the role of sporting events in the propagation of an epidemic was experienced in the spring of the latter year.
Methods: Mandatory measles case reports were requested from all high schools in Niigata, which covered a school year, date of onset, club activity, vaccination status, and hospitalization.
Results: With national marathon and kendo (Japanese fencing) meetings for high school students, measles outbreaks occurred at 27 high schools with 192 patients (186 students and 6 teachers) in Niigata. Of 64 unvaccinated patients, 14 (21.9%) were hospitalized and 6 (6.2%) of 97 vaccinated patients. Mostly single cases were encountered at high schools in which index cases had a vaccination history, whereas at a high school in which index cases had no vaccination history, the total number of cases per school increased, mostly within more than 3 cases (p<0.05).
Conclusion: We conclude that sporting events, even if outdoors, might be a risk factor for measles infections. Appropriate actions to control outbreaks should be performed promptly in collaboration with related personnel and institutions.