None of the cases were near Perote, which received a flurry of media attention shortly after the outbreak surfaced because it had what then looked like the earliest cases and the large hog farms in the area. (sciencemag.org)
The most sensitive detector of hog farm air pollution, he adds, is still the human nose. (sciencemag.org)
In North Carolina, these are areas downstream from hog farming operations, and in Maryland, downstream from large chicken farms. (scientificamerican.com)