The incidence of rabies in animals has decreased dramatically over the last 60 years.  In the 1930’s, there were several human cases of rabies per year, usually acquired from dog bites.  In the mid 1950’s, an extensive campaign to vaccinate dogs in Michigan against rabies caused the incidence of this disease to decrease to a point where even one case per year is out of the ordinary.  The last case of human rabies in Michigan was reported in Hillsdale County in 1983, likely acquired from contact with a rabid bat.  Prior to this, there had not been a case of human rabies in Michigan since 1948.  Today, bats and skunks can carry rabies in Michigan, sometimes transmitting the virus to other species.  Any rabid animal, regardless of its source of infection, can transmit rabies to humans.  Dogs and cats are still frequently tested for rabies following bite incidents involving humans but they rarely test positive.  

The graphs below illustrate trends in animals testing positive for rabies in Michigan. 

[Left] Animals testing positive for rabies from 1938 to 2005, which includes individual animal species.  [Right] Animals testing positive for rabies from 1950 to 2005, which is classified by whether the animal is wild or domestic.

Bats are the animal most frequently testing positive for rabies in Michigan.  The prevalence of rabies in Michigan’s bat population is probably less than 1%, however, 4-6% of bats submitted for testing following a potential human or unvaccinated pet exposure test positive for rabies [See Graph Below].

The number of animals submitted for testing following a potential rabies exposure increases in the spring.  The highest submissions occur in the summer months of June, July, and August, following a period of decreasing submissions [See graph below].  In the winter, potential rabies exposures and laboratory submissions are at their lowest levels.  Geographically, bat rabies is generally wide spread across the Lower Peninsula of Michigan, although cases do occur in the Upper Peninsula.  As can be seen in the map below, terrestrial rabies in wild animals is mainly restricted to the southeastern region of the state.