The most common transmission is when animals, or humans directly in charge of the animals, move between premises. That's the number one thing that you're shutting down with biosecurity.
In 2014, certainly one of the possible introductions—and it was pretty high on the list as a possible introduction—was the fact that there were B.C. Hydro vehicles going through fields. They were going from farm to farm through fields, putting in something.
In 2014, it was a strain of pathogenic avian influenza that was coming directly from wild animals, and I'm pretty sure that they basically carried duck poop from one farm to another farm and continued the infection. Something takes it onto the farm, and then someone takes it onto the barn, so yes, it could have been that a farm worker accidentally took it into the barn by not being careful or not changing footwear in a barn, but the introduction onto the property was actually thought to be transmitted by vehicles.
There are so many different things, and that's why, when you do an epidemiological investigation of what caused it and how it moved from here to there, you never really get the final answer. You're so lucky if you get that smoking gun. You get that it could have been this or it could have been that. When you're posed with whether it could be this threat, for someone who is unaware of the biosecurity measures that should be taken and isn't taking them, we don't know where they've come from and where they're going. That's a clear threat to me, because there are so many things that can do it. If you can say no to something that clearly would cause a problem, that's helpful.
When there are so many things—will wind carry it, will dogs carry it, do birds carry it, do insects carry it—you never know. Some things you can't stop, but if there's something you can stop, why would you not stop it?