Impacts of FMD differ from one kind of animal to another. Sheep tend to carry the infection without showing symptoms. Cattle suffer openly and pass the virus to one another by direct contact (say, muzzle to muzzle) or vertically (cow to calf) by suckling. Pigs are special: They excrete far more of the virus than other livestock, and over a longer period of time, broadcasting it prodigiously in their respiratory exhalations. They sneeze it, they chuff it, they oink it, they wheeze it and burp it and cough it into the air. One experimental study found that pig breath carried thirty times as much
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