Last week, I had the great pleasure of presenting our recent work on the 2016–17 Arkansas mumps outbreak at the Massachusetts Department of Public Health. In case you missed it, you can find our short paper in the Lancet ID here. I also wrote up a blog post explaining the basics of our process at NPR and did a radio interview with NPR-affiliate station KUAF, which can be found here and here.
As usual, I’ve uploaded a PDF copy of the slides, which you can download here. I’ve also set up a slideshow below:
Though I mention this briefly in the slides, I wanted to highlight one interesting issue (and opportunity for follow-up work) pertaining to this outbreak that I’ve been thinking about lately: namely, the role of disease transmission in immigrant communities. The 2016–17 Arkansas mumps outbreak seems to have gotten its start in the state’s Marshallese community – a community characterized by densely-packed living quarters that may have elevated the force of infection associated with mumps. If this is the case, this particular community may not be well-represented by pre-vaccination era estimates of mumps transmissibility parameters (like the basic reproductive number), which were often modeled using data from European and North American school-going children.
We need individual-level vaccination data (as well as ethnicity-specific case counts over time) to pursue this line of inquiry further and approximate the basic reproductive number in the affected Marshallese community*. Thankfully, the Arkansas Department of Health is collecting these data, and I’m hopeful that we can see this follow-up work to fruition when they publish their findings!
*It should be noted that the outbreak wasn’t confined exclusively to this community. This suggests that while increased force of infection may have been a key factor in accelerated disease transmission among the Marshallese, more conventional explanations (like inadequate vaccination coverage or vaccine failure) likely played a critical role, too – especially among affected non-immigrant communities. Inadequate vaccination coverage is essentially what we posit in our Lancet ID short paper, but because we didn’t have ethnicity data available to us, we were limited to using averages across all communities that experienced mumps transmission during the outbreak. However, soon after publication, we discovered that Northwest and Central Arkansas – the regions hardest-hit by the 2016–17 outbreak – are also uniquely plagued by vaccine refusal, which provides some compelling empirical evidence for our findings – despite the aforementioned limitations. Nevertheless, we’re eager to get started on follow-up work that more deeply explores the underlying heterogeneities discussed in this blog post!