Stuart , the problem with checking for viruses, it would cost £100's for 1 test(or that is what it was approx when I was working for individual testing) I had heard of a fancier who had youngsters die overnight, sent them for testing, to be told they could find nothing wrong. Before those results came back I told folk what the answer would be as they would not normally send them to a virology laboratory for further tests. What I think is required is to test for avian viruses with a virologist not a vet to find what this/these viruses are. This would require major funding. Cheers John b