Like the mumps outbreaks that occurred in 2006 (2), much of the current outbreak is occurring in congregate settings, where prolonged, close contact among persons might be facilitating transmission. Within the affected religious community, cases have occurred predominantly among school-aged boys, who attend separate schools from girls. The higher rate among boys might be a result of the additional hours that boys in this community spend in school compared with girls, including long periods in large study halls, often face-to-face with a study partner.
In addition, transmission in the community overall might be facilitated by relatively large household sizes. According to the 2000 U.S. Census, the mean household size in one of the affected communities was 5.7, compared with a mean U.S. household size of 2.6. The limited transmission to persons outside the community might be a result of the relatively less interpersonal contact between persons inside and outside the community.
Although the school settings and large household sizes might be promoting transmission, the high vaccination coverage in the affected community likely is limiting the size of the outbreak. In addition, high vaccination coverage in surrounding communities is the most plausible reason that the few cases outside of the affected community have not caused other outbreaks.
PlagueBlog recommends letting the boys out for recess more frequently and sending them home earlier, poor things.