we havn't had YBS for a couple of seasons now , noticed some of the first symptoms mentioned , them not interested in coming in after flying out another to look out for is green slimy droppings , we must deal with it at the earliest stage possible .if they get as far as the throwing up stage they need to be removed that is if you can see which bird is doing the throwing up . not wanting to say I have the miracle cure ( to stong a statement ) but worked for us and its not a pigeon product that you pay an arm and a leg for , not going to post it on an open post , and for the record we fly our young birds , winning all ybird trophys points ave and all the local 2bird races this past year not as good the returns as we would of liked but there was other problems in the skys this year more than previous years