It is now understood the sheep at the centre of the alert have shown clinical signs of foot and mouth and, although it will be three days before tests will show if they have the disease, people are already preparing themselves for the worst.
Four hundred gardai are on duty along the border after a suspected outbreak of foot and mouth in south Armagh. A five mile exclusion zone has been imposed around the farm, close to the village of Meigh, where vets are preparing to incinerate a flock of sheep.
The North's Agriculture Minister Brid Rogers is appealing for calm but there can be no hiding from the potential disaster that may lie ahead on both sides of the border.
The sheep in south Armagh were brought from a market in Carlisle two weeks ago for slaughter but instead were sold on live to a south Armagh farmer. Other sheep from the same batch were sold on to a cattle dealer from the Republic and it is feared they have crossed the border.
The hunt is now on, but they may have already infected others.