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Repeated introductions and intensive community transmission fueled a mumps virus outbreak in Washington State
Louise H Moncla1, Allison Black1,2, Chas DeBolt3
1Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, United States.
Abstract:
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.
Insights
A 2016/2017 mumps outbreak in Washington was driven by introductions from other states and sustained by transmission within the Marshallese community, highlighting the role of social networks in disease spread.
Area of Science:
- Epidemiology
- Genomics
- Public Health
Background:
- Despite high childhood vaccination rates, Washington State faced a significant mumps outbreak in 2016/2017.
- Cases were disproportionately observed in school-aged children and the Marshallese community.
Purpose of the Study:
- To investigate the origins and transmission dynamics of the 2016/2017 mumps outbreak in Washington State.
- To utilize genomic sequencing to trace viral introductions and identify key transmission networks.
Main Methods:
- Whole-genome sequencing of 166 mumps virus samples from Washington and other US states.
- Phylogenetic analysis to reconstruct viral introductions and transmission chains.
- Epidemiological data analysis to correlate with genomic findings.
Main Results:
- Approximately 13 mumps introductions into Washington were identified, primarily originating from Arkansas.
- Multiple, co-circulating transmission chains were established within the state.
- Transmission was predominantly sustained within the Marshallese community, indicating the importance of social contact structures.
Conclusions:
- Genomic data are crucial for understanding outbreak epidemiology and identifying transmission drivers.
- Contact networks and historical disparities can increase vulnerability to infectious diseases, even with effective vaccination.
- Targeted public health interventions may be necessary for high-risk communities during outbreaks.
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