here is some interesting information on Coronavirus courtesy of Sue Ives the President of VAOBA.

Coronavirus does have carrier animals (animals that do not show any signs of disease but carry it). Winter dysentery of cattle is "easily carried on shoes, clothes or fomites" (objects) so it looks like it would be very easy to bring home from an alpaca show even if you did not take alpacas to the show.

Coronavirus is common in alpacas and was associated with diarrhea in adults and young animals in the fall of 2005 or 2006 associated with shows in the northeast but I think it is pretty much everywhere. In my experience, the tests run in labs in VA are negative but testing with electron microscopy at Texas A & M will pick it up (a virologist at Cornell told me to send poop samples to TxAM).

The coronavirus is found in the respiratory or GI tract, but virus isolation is not easy. It is gonna be a really tough thing to prevent spread if you have a carrier animal coming back from the show. It is not clear how long the animal might carry the virus. Apparently it is more of a problem when in conjunction with other diseases or stressors.

That being said, I think quarantine of 2-4 weeks is good but must involve different clothing and shoes from the quarantine animals to the healthy. Minimize other diseases (parasites, etc,) and stresses and that is all you can do. Some farms have their "show string" animals in a completely different area from the non show animals to avoid bringing things home any unexpected "visitors" but this is a luxury not everyone can accommodate.