Porcine epidemic diarrhea virus is still circulating in the U.S., according to Paul Sundberg, DVM, executive director of the Swine Health Information Center. Noting lowered incidence, he says improved biosecurity and a buildup of natural immunity by exposed herds have helped reduce the level of PED. This natural immunity may be short lived, however.
Source: The Pig Site, January 29, 2016.
The biggest recommendation is to work with a veterinarian and implement a secure and rigid biosecurity plan. Not just develop one but actually to implement it, to make sure that everybody coming on the farm, everybody that deals with the pigs, any of the traffic, anything that happens on the farm as far as inputs, goes through a biosecurity protocol.