Is rabies alive in Massachusetts?

By Mandi Cai

I have an unhealthy habit of petting stray cats. They roam around my neighborhood in Cambridge, they're friendly, and I like to pet them on my way home from work every day. It's not the best idea, but I had no reason to stop receiving their affection, until recently.

A couple months ago, I was petting a particularly erratic and jumpy teenage cat. It nipped me while playing, and my friend at the time remarked: "Hey, you might want to be careful. Rabies is a thing."

That statement got me thinking: "Is rabies still a thing?" A lot of people believe it to be an illness of the past - coming across a rabid animal is not a common experience anymore, nor is contracting the rabies virus itself. 25 minutes of thorough hand washing, 9 phone calls, numerous WebMD and Reddit threads, and 5 public datasets later, I was able to get a better picture of the current rabies landscape in Massachusetts (spoiler: cats are not common carriers of rabies, although there is always a chance that they'll come into contact with rabid animals). Phew!

My peace of mind came primarily from, which offers several public data sets including the yearly reports on rabid animals throughout Massachusetts. Let's take a look:

Which animals are rabid?

Percentage of each animal in the pool of 624 rabid animals, 2013 - 2017

Across all 5 years, raccoons make up the highest percentage of rabid animals accounted for in MA.

Skunks and bats alternate as the animal with the second highest percentage.

We can also view the percentages of each animal as layers.

It's pretty clear that raccoons, skunks, and bats have shared a large portion of the rabid animal pool in MA.

What if we took a look at the ratio of reported animals to rabid animals across all 4 years?

Each year, around 400-500 dogs are submitted for rabies testing, but none have been found rabid. Dog owners must comply with the mandatory rabies shots required by MA law for cats and dogs.

However, any dog involved in a biting incident must be quarantined for 10 days. An animal control officer will determine during this period of observation whether the dog needs rabies treatment.

Around 600-700 cats are submitted for rabies testing each year. Cats are often left outside to roam, and are thus exposed more frequently to common carriers of rabies such as raccoons, skunks, and bats.

Bats are by the far the most submitted animal for rabies testing. Around 900-1000 bats are submitted each year.

Bats are known (and sensationalized) as rabies carriers, which would attribute to the high number of submitted bats. It is also better to err on the side of caution with bats because their bites can go undetected. also provides the numbers of animals reported and positive for rabies by county. Different species may occupy habitats of differing square footage and have varying migratory patterns.

For example, foxes can "actively maintain territories that may vary in size from 2 to 7 square miles", according to They enjoy spending time in the intersections of forests, fields, and thickets. Bats will occupy buildings and trees in the summer and move to caves or migrate elsewhere in the winter. The 9 different species of bats native to Massachusetts can be found all over the state.

Let's inspect the different counties in Massachusetts and the rabid animals reported in each from 2013 to 2017.

Across counties in 2017 ...

In 2017, Worcester County had 366 animals submitted for rabies testing and 22 animals were found positive. Coming in at a close second, Essex County had 287 animals submitted, and 15 animals tested positive.

Each circle represents the reported animals that tested positive for rabies in that county.

Rabid animals across counties in 2017

Across counties from 2013 to 2017 ...

Each overlaid circle on a county represents a single year's worth of reported animals that tested positive for rabies. Worcester and Middlesex both accumulated high numbers of reported rabid animals over the years.

Rabid animals across counties 2013-2017

Sources Rabies surveillance data Rabies Clinics Learn about foxes Bats of Massachusetts

I used Cloudflare Design's accessible color palette generator to generate the color scheme.

I also used Russell Goldenberg's Scrollama library to create the scrolly story.

More of my work here.