The new virus, Porcine Epidemic Diarrhea Virus, has now spread to 13 states, reports Montserrat Torremorell, the Allen D. Leman Chair in Swine Health and Productivity at the University of Minnesota's College of Veterinary Medicine.
Torremorell says there have been more than 100 cases positively identified as the virus.
It first showed up in China where more than one million pigs died.
The U.S. hog industry has been on high alert, warned to practice tight biosecurity to prevent the spread of the virus that is particularly deadly to piglets.
It does not affect people.
Canadians, including the Canadian Food Inspection Agency, various hog-industry associations and swine veterinarians, have been repeatedly warning farmers and anyone connected to hog production to be extremely careful to avoid bringing the virus into the country.