Community Testing

Community Spread in Massachusetts – Part II

What a day, as we learn Trump tested positive for the coronavirus. No further comment is necessary on that. But here’s a trivia question for you. Over the two week period ending September 26, what Massachusetts community had the highest per capita Covid testing rate? Stop. Before you read on, think about it. Is it Chelsea, or Everett, or Lowell, or another one of the hot spot communities in Massachusetts? Is it Boston, because of the many medical centers located there? No.

As Table 1 shows, the big winner is Williamstown, home to Williams College.  More than 4% of Williamstown’s population is being tested each day for coronavirus.  Of course, this figure is somewhat distorted, as many of those tested are presumably students who are not included in Williamstown’s stated population.  But even if one assumes that all of Williams College’s students (about 2,000) were back on campus, the per capita testing rate is astounding.

And there was even more testing being done in Williamstown for the two weeks ending September 19th, as it had the largest dropoff in testing from week to week.  In all, nine of the top ten per capita testing communities are home to college and universities. And even Somerville’s inclusion might partially reflect testing associated with Tufts. (In the original version of this post, I had stated that Dudley was a outlier, because I didn’t realize that it is home to Nichols College, which has done extensive testing.  Thanks to Jen for pointing out the error).


Table 1: Per Capita Massachusetts Testing Statistics
Most Testing and Largest Testing Changes
Week over Week Ending September 26,2020
Two Weeks Ending 9/26/20   Weekly Change Ending 9/26/20
City/Town Daily Tests per 100,000   City/Town Largest Increase in Daily Tests Per 100,000   City/Town Smallest Increase in Daily Tests Per 100,000
Williamstown 4,211   Southborough 431   Williamstown -796
Amherst 3,856   Cambridge 421   Nantucket -105
Cambridge 2,622   Newton 401   Somerset -10
Wellesley 2,328   North Andover 379   Charlton -8
Somerville 2,103   Boston 282   Peabody -7
North Andover 1,968   Somerville 263   Yarmouth -4
Norton 1,944   Dedham 259   Rowley -2
Boston 1,845   Brookline 250   N. Attleborough 4
Dudley 1,806   Wellesley 196   Wrentham 5
Waltham 1,684   Chelsea 158   Westport 6


One technical point. It is possible, although unlikely, that there are communities in Massachusetts with higher testing rates than shown here. Why? I am using population estimates that are embedded in the weekly report itself (it can be derived from the daily incident rate and the number of cases). But if there are fewer than five cases, the state suppresses the exact number, so I can’t derive a population estimate. In fact, of the 351 communities in Massachusetts covered in the report, I can’t calculate a population for over half. I could try to pull population estimates from other sources and integrate them into this analysis, but I think it highly unlikely this will add any community to the top ten list (and I’m lazy).

One other point related to the blog itself. As I noted when I first started, I’ve never blogged before. I’m learning as I go. And I noticed yesterday’s post via email, on a tablet, or on cell phone has strange formatting or the numbers weren’t visible through the colors. I am trying to learn how better to format the posts, but for now, if you flip your device to landscape mode, the posts become more readable (and I’ve bolded the numbers within colored cells).

5 replies on “Community Spread in Massachusetts – Part II”

This is a great source of non-bias information on Covid and our state. Thanks. Based on number trends what is causing the general increase in positive cases? More testing, colleges returning, to much partying, or the beginning of community spread?

Well, I definitely do not think it has to do with the return of college students. In general, the positivity rates associated with colleges have been very low. Is it more testing? I’m not an epidemiologist, but the most telling statistic in my mind is the increasing positivity rate, which means that the number of cases would increase even with no more testing. My guess is that after the summer ended, people began higher levels of indoor interaction, and, additionally, as this becomes the “new normal”, become more relaxed about safety protocols. There is one further factor, at least in the community in which I live: people make the erroneous assumption that their friends can’t possibly be asymptomatic carriers, because the friends “are careful”. Carefulness is completely in the eye of the beholder. Your version of “careful” is quite likely to be different than my version of “careful”.

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