Swine Flu in the Talmud

They once said to Rav Yehudah: There is a deadly plague among the pigs. He decreed a fast, even though Jews would not be directly affected by the destruction of pigs.

The Gemara asks: Shall we say that Rav Yehudah holds that a plague which is visited on one species of animal is apt to be visited on all species of animals? Thus, kosher livestock were threatened by the plague that struck pigs.

The Gemara answers: No. Pigs are different, in that their digestive tracts resemble those of humans. Therefore a plague that strikes pigs bodes ill for the people of that place, which is why Rav Yehudah decreed a fast. 

b.Taanis 21b (ArtScroll Schottenstein Edition)