Porcine epidemic diarrhea virus, deadly only to young pigs and no food safety risk or danger to humans, appeared in the United States for the first time last spring in Ohio and within weeks had spread to four other states.

First surfacing in Britain more than 40 years ago, the virus has spread throughout Europe and Asia. It has caused problems most recently among pork producers in China, where a 2012 strand of the disease was 99.4 percent similar to cases now found in the United States, according to researchers.

For more, read Hog Producers Battling to Contain Virus That Has Killed Piglets by the Thousands (New York Times).