In each of the following passages,
a. What data are to be explained?
b. What hypotheses are proposed to explain them?
c. Evaluate the hypotheses in terms of the criteria presented in Section 13.3, pp. 564–566.

Monkeypox, a viral disease related to smallpox but less infectious and less deadly, was detected for the first time in the Americas in 2003. At least 20 cases have been reported, in three Midwestern states, Wisconsin, Illinois and Indiana, according to the Centers for Disease Control and Prevention.
The patients ranged in age from 4 to 48, and became ill between 15 May and 3 June, 2003. All had direct or close contact with ill prairie dogs, which have become common household pets, and which might have caught monkeypox from another species, possibly Gambian giant pouched rats, which are imported as pets from West or Central Africa, where the disease had long occurred. Monkeypox in Africa is carried mainly by squirrels but is named after monkeys because it often kills them.
Several patients in the American outbreak work for veterinarians or pet stores that sold prairie dogs and Gambian rats. By quickly identifying the animals that can be infected with monkeypox, health officials hope to eliminate them before the disease becomes endemic in the Americas.
—Reported in the The New York Times , 9 June 2003