I think the risk to an individual farmer who has someone come into their barn with their animals, and where they have their family, can be significant.
You already identified the risk of bringing in the disease. That depends a lot on where those individuals have been in the past 24 or 48 hours, what they've been exposed to and how close they can get to the animals in the barn, whether they touch them or they're just at the door taking pictures. That one is much more murky to me.
However, I would not want to leave, for a minute, the impression that I don't think there are risks.