There's no absolute with infectious diseases. That's the big issue. We can't say zero. I could say that the risk, apart from mink and COVID, is probably very low. We're not going to see avian influenza introduced by someone walking onto a farm.
There are potential risks; the infectious disease risk actually is much greater to the person who goes on the farm, who may pick up something there. There are risks, and there are always going to be risks when people come in. They're going to be higher if somebody is going from farm to farm. They're going to be higher depending on the type of contact. You don't need long or prolonged contact; you need the right bacteria and virus parasite for transmission. However, the odds of a person bringing that in are really low.
We're certainly not going to say it's zero; I'm going to say it's quite low. There are other more important reasons for preventing trespass than biosecurity, even though I think biosecurity still is an important issue.