Nota de InvestigacónBulgaria has a surveillance program on avian influenza to keep a close watch on health of poultry, exotic birds, and wild birds. The samples include sera for serologic examination, and carcasses, tissue samples, tracheal and cloacal swabs, and feces for virologic examination. The number of samples depends on the epizootic situation in the country and in neighboring countries. Mmigration and resting and living areas of wild birds also are under consideration. The territory of Bulgaria is divided into 28 regions. For each of these regions, there are exact types and numbers of samples, depending on latitude, water reservoir, farms, and backyards. Since October 2005, surveillance has become harder because of the situation in Romania and Turkey. Since 2006, the number of samples has vastly increased.