Porcine Epidemic Diarrhea was first identified in the US mid-May and testing of samples collected since last December has revealed the infection has been present in the US since at least mid-April.

Dr Paul Sundberg, the vice president science and technology with the National Pork Board, reports by the week of June 16 the infection had spread to approximately 250 sites from Ohio to Colorado and Minnesota down to Oklahoma but the rate of spread has been very region-specific.

Dr Paul Sundberg-National Pork Board

There are sites in some mid western states that have been positive and there just has been no spread that we know of to neighbouuring herds.

There's no lab reports nor veterinarian reports of spread to neighboring herds so that's very information.

That's very good news.

There are though in other areas laboratory and veterinary reports both where the virus was first identified in a farm and it has moved very quickly from farm to farm.

Part of the issue we have with this is trying to understand those differences.

What's going on in one area or one region versus the other region and we're working with the USDA Centre for Epidemiology and Animal Health in Fort Collins and the University of Minnesota on an epidemiological survey so we can try to understand better those regional differences.

In some places, it's spreading very quickly and in other places, it's not spreading at all and that's what we need to understand about the infection as it's occurring right now.

Dr Sundberg says, while the economic impact on affected sites where farrowing losses have reached 100 per cent has been devastating, it is to early to calculate the industry-wide economic impact.