Bornavirus remains a mystery. As Sarah said, many people probably have a "positive" bird and don't even know it because of no symptoms. There are reputed to be several strains with varying degrees of severity; the bornavirus test itself is suspect and known to give false positives. However, since your bird is vomiting, it obviously has something going on. You've received good medical advice from Sarah and Mary Lynn; I can't add to that. Hang in there and deal with one day at a time. You're on a rollercoaster ride with days good and bad to come. I feel for you.