Michael Yezzi raises 1,000 pigs a year in Shushan, N.Y. He's worried about how to keep his farm safe from a disease that has no proven cure. Abbie Fentress Swanson for NPR hide caption

itoggle caption Abbie Fentress Swanson for NPR

France has banned imports of live pigs and other products from the U.S. to keep out a virus that has killed more than 4 million pigs in the U.S. Here, young pigs look out of a pen at a North Dakota hog farm in a 2005 file photo. Will Kincaid/AP hide caption

itoggle caption Will Kincaid/AP

Piglets at Hilldale Farm in State Center, Iowa in March 2013, just before porcine epidemic diarrhea began spreading through hog farms in the U.S. Amy Mayer/Harvest Public Media hide caption

itoggle caption Amy Mayer/Harvest Public Media

In recent years, pork producers have found ways to keep the animals healthy through improved hygiene. M. Spencer Green/AP hide caption

itoggle caption M. Spencer Green/AP

William von Schneidau, who owns the BB Ranch butcher shop at Pike Place Market in Seattle, has made prosciutto from pigs fed marijuana. Courtesy of BB Ranch hide caption

itoggle caption Courtesy of BB Ranch

Berkshire pigs on Happy Hula Farm, a member of the Eden Farms collective. Amy Mayer/Iowa Public Radio hide caption

itoggle caption Amy Mayer/Iowa Public Radio

Villagers gather dead pigs in Jiaxing, in eastern China's Zhejiang province, on Wednesday. The number of dead pigs found in Shanghai's main river had doubled in two days to more than 6,000, the government said. AFP/AFP/Getty Images hide caption

itoggle caption AFP/AFP/Getty Images

A Russian sow on Mark Baker's farm. Four other parties have joined Baker's lawsuit against the Michigan Department of Natural Resources. Courtesy of Long Haul Productions hide caption

itoggle caption Courtesy of Long Haul Productions