Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, United States
Allison Black
Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, United States; Department of Epidemiology, University of Washington, Seattle, United States
Chas DeBolt
Office of Communicable Disease Epidemiology, Washington State Department of Health, Shoreline, United States
Misty Lang
Office of Communicable Disease Epidemiology, Washington State Department of Health, Shoreline, United States
Nicholas R Graff
Office of Communicable Disease Epidemiology, Washington State Department of Health, Shoreline, United States
Ailyn C Pérez-Osorio
Office of Communicable Disease Epidemiology, Washington State Department of Health, Shoreline, United States
Nicola F Müller
Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, United States
Dirk Haselow
Arkansas Department of Health, Little Rock, United States
Scott Lindquist
Office of Communicable Disease Epidemiology, Washington State Department of Health, Shoreline, United States
Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, United States; Department of Epidemiology, University of Washington, Seattle, United States
In 2016/2017, Washington State experienced a mumps outbreak despite high childhood vaccination rates, with cases more frequently detected among school-aged children and members of the Marshallese community. We sequenced 166 mumps virus genomes collected in Washington and other US states, and traced mumps introductions and transmission within Washington. We uncover that mumps was introduced into Washington approximately 13 times, primarily from Arkansas, sparking multiple co-circulating transmission chains. Although age and vaccination status may have impacted transmission, our data set could not quantify their precise effects. Instead, the outbreak in Washington was overwhelmingly sustained by transmission within the Marshallese community. Our findings underscore the utility of genomic data to clarify epidemiologic factors driving transmission and pinpoint contact networks as critical for mumps transmission. These results imply that contact structures and historic disparities may leave populations at increased risk for respiratory virus disease even when a vaccine is effective and widely used.
