Avian Influenza, or bird flu, refers to a disease caused by a virus that is adapted to survive in avian (bird) intestines. The birds that carry the virus are not necessarily made sick by it. The virus occurs worldwide and is highly contagious once a bird does become sick by it. The virus can then be passed to another bird through feces, urine, or saliva. The disease can be passed to birds in captivity through dirty cages or other items that have been used to handle infected birds. The infection can range in its effects from mild symptoms like ruffled feathers and lower egg production to fatality in the worst cases. Typically, the virus does not attack people, but it is possible and has been reported in several instances in the recent past in Asia and Europe. To date, there is no effective treatment for humans that are infected. Experts are monitoring the avian influenza situation carefully for any new developments.