Scientists studying a leprosy outbreak in medieval England believe they may have found the culprit: squirrels. More specifically, they suggest that the squirrel pelt trade could have brought this disease to England from Scandinavia.
In examining the skull of a medieval woman from East Anglia, scientists have identified damage to the skull caused by facial lesions, and have also found evidence of a strain of Mycobacterium leprae, the bacteria that causes leprosy, in the DNA contained within the bone.
While it is possible that the leprosy that became prevalent in England during the medieval era may not have come from squirrels, the animals are known to carry the disease, even to the present day. And there have been cases where leprosy has been contracted by humans after coming into contact with animals infected with the disease. Some doubt that the bacteria could have remained on pelts or in squirrel meat for the time it would have taken to transport these goods from Scandinavia to England, but others note that some people kept squirrels as pets, which would have increased the lifespan of the bacteria and the chances for transfer between the species.
You can read more about the possibility that cute woodland creatures brought leprosy outbreaks to England here.