Case Prevalence Per 10,000, By Town

For the week ending March 31, 2021


Once again this week cases of COVID-19 in Connecticut increased, making this the fourth consecutive week of rising case numbers. The more contagious variant first found in Britain continues to be the likely cause.

Unlike last week, however, the spread is not happening everywhere around the state. In fact, just under half of Connecticut’s 169 towns actually saw a decrease in case numbers.

Case numbers rose from 7,694 for the week ending March 24 to 8,866 for the week ending March 30, an increase of 1,172, or 15.23%. This is a smaller increase than we saw last week, when case numbers jumped by 2,023. Case prevalence, or the number of cases per 10,000 people, rose statewide from 21.53 to 24.81. Case positivity also rose from 3.48% to 3.65%, but despite this small increase the state is likely still identifying the lion’s share of the new cases.

This increase comes as two major events are happening; the re-opening of most of the state’s economy, and the expansion of vaccine availability to everyone over age 16. Gov. Ned Lamont says he is watching numbers closely, but he has not made any moves to reimpose stricter controls on stores, restaurants, and other businesses and services.

Looking at the map, last week’s trend of higher prevalence numbers in the southwestern third of the state continues to be visible on the map, but there are many more exceptions to the pattern this week than last. High-prevalence towns are clustered in the Waterbury and Danbury areas, both of which have long struggled with containing the pandemic, and the lower Naugatuck Valley. The number of towns with prevalence numbers above 40 cases per 10,000 people increased this week from six to 14.

However, as I was creating this map, I noticed something unusual: there were nearly as many towns that had a decrease in cases as had an increase. In fact, while 89 towns had an increase in case numbers, 80, or nearly half, saw either a decrease in new cases or no new cases at all.

The towns that recorded an increase totaled 1,689 new cases. 46% of that increase, or 776 new cases, came from only 10 towns: Bridgeport (118), New Haven (108), Waterbury (106), Danbury (99), Stamford (73), Bristol (63), Greenwich (55), Naugatuck (54), Hartford (52), and New Britain (48). Unsurprisingly, all of the state’s largest cities, along with a few of the larger towns, are on this list.

It may, then, be more useful to track where case prevalence is expanding or contracting, and by how much. To do that, I created a map labeling each town with the increase or decrease in case prevalence and color-coded each one.

Case Prevalence Increase or Decrease Per 10,000, By Town

For the week ending March 31, 2021

This map shows that COVID-19 is currently spreading more rapidly relative to population in different spots all over the state. Some, like Danbury, are cities. Others, like Darien, New Milford, East Haven, and Wallingford, are large suburbs. But some, like Ellington, Middlefield, and Sprague, are mainly rural.

Decreases in case prevalence are similarly widespread. Some are cities, like Derby and Ansonia, which are recovering from a spike in cases over the last few weeks. But many others are wealthier suburbs or rural towns, like Ridgefield, Salem, and East Granby. Altogether, the towns that saw a decrease in cases and case prevalence were responsible for a statewide decrease of 533 cases.

What does this mean? It’s possible that this is a sign of another plateau in case numbers approaching. When there is a significant increase or decrease in cases, it tends to happen either all over the state at once or concentrated in a very specific and highly visible region. A mixed bag like this may mean that the weeks of increases are slowly coming to an end.

This could also be an anomaly. But as more and more people are vaccinated, this kind of push and pull between more contagious variants of the virus and immunity may produce more results like this. We’ll know more next week.

Here is last week’s map for comparison:

Case Prevalence Per 10,000, By Town

For the week ending March 24, 2021

Susan Bigelow is an award-winning columnist and the founder of CTLocalPolitics. She lives in Enfield with her wife and their cats.

The views, opinions, positions, or strategies expressed by the author are theirs alone, and do not necessarily reflect the views, opinions, or positions of

Susan Bigelow

Susan Bigelow is an award-winning columnist and the founder of CTLocalPolitics. She lives in Enfield with her wife and their cats.