Wait a minute. Tylan is an antibiotic. If it's viral, no antibiotic will do a thing. You have no idea what you're treating. Could be bacterial, viral or fungal. Viruses will not be affected by antibiotics. Antibiotics will only treat symptoms of bacterial, however, if it's a disease that leaves the bird a carrier, it won't change that status. The bird will remain a carrier like a Typhoid Mary in the flock. Forewarned is forearmed. This is why breeders euthanize birds who show contagious respiratory symptoms.