According to the New York Times, so far seventeen people in Wisconsin, ten in Indiana, and one in Illinois have become infected, but the rate of reported infection is expected to rise as people become familiar with the symptoms and seek treatment. The means of transmission are not well understood, making it difficult to be certain that the disease is contained. So far, however, there have been no documented cases of human-to-human transmission in the U.S., as all of those infected have had direct contact with prairie dogs.
This is yet another reason why it’s best to stick with domesticated animals when looking for a pet for your kids.