Measles outbreaks in the United States continue to occur in subpopulations with 
sufficient numbers of undervaccinated individuals, with a 2014 outbreak in Amish 
communities in Ohio pushing the annual cases to the highest national number 
reported in the last 20 years. We adapted an individual-based model developed to 
explore potential poliovirus transmission in the North American Amish to 
characterize a 1988 measles outbreak in the Pennsylvania Amish and the 2014 
outbreak in the Ohio Amish. We explored the impact of the 2014 outbreak response 
compared to no or partial response. Measles can spread very rapidly in an 
underimmunized subpopulation like the North American Amish, with the potential 
for national spread within a year or so in the absence of outbreak response. 
Vaccination efforts significantly reduced the transmission of measles and the 
expected number of cases. Until global eradication, measles importations will 
continue to pose a threat to clusters of underimmunized individuals in the 
United States. Aggressive outbreak response efforts in Ohio probably prevented 
widespread transmission of measles within the entire North American Amish.