Part of our Losing to Lyme series
Lyme disease is a big — and growing — problem in Massachusetts. Here's how the number of cases has risen over the last 12 years:
A few important notes on the data:
- In 2012, the state started counting confirmed and probable cases of Lyme disease, which is why there's a clear jump that year.
- Data is compiled based on "passive surveillance," which means the state counts reports of positive tests from laboratories, and also waits on health providers to report probable Lyme disease cases.
- Other factors can affect Lyme cases, such as the drought conditions from spring 2015 to the spring of this year, because that can affect the numbers of ticks.
- The CDC estimates that just 10 percent of cases of Lyme disease are actually reported, so the actual prevalence of disease is much higher.
Below is a county-by-county look at those cases. The map has three views:
- The default view shows cases of Lyme disease per 100,000 residents. In this view, you can see that the biggest risk is on Martha's Vineyard and Nantucket.
- The second view shows percent change in cases. Here, you can see how Lyme disease is getting worse, particularly in Bristol County, and also in Suffolk County and central Massachusetts.
- The third view shows overall numbers of cases, and makes it clear that Lyme disease is most acutely an eastern Massachusetts issue.
With reporting by WBUR's Benjamin Swasey