MANHATTAN, Kan. — The number of pigs and hogs in the United States is the lowest it's been in seven years, according to a new report from the U.S. Department of Agriculture.

One of the main reasons for the decrease is a virus that's been killing almost 100 percent of the baby pigs it infects. It's called porcine epidemic diarrhea virus, or PED, and it entered the United States for the first time in May 2013.

Kansas State University swine specialist Steve Dritz says the virus has now spread to Canada. He and fellow researchers at the university are studying ways the virus is spreading. Dritz says the feed the baby pigs are eating may be contributing to the spread of the disease.

"There is evidence that the virus was active in an ingredient in the feed," Dritz said. "Although that ingredient was in the feed, there is no evidence that the feed itself was infective."

Researchers know the main way the virus is spread is through the pig's fecal matter. The amount of virus spread through the pig's food has yet to be determined. Dritz says this virus poses a particular challenge since it is so new to the United States.

"It's a really, really difficult thing because from a diagnostic standpoint, the procedures and protocols and things to detect the virus are very new," Dritz said.

The research team is currently applying for funding to advance their research on the virus.