ABSTRACTKI Polyomavirus (KI PyV) has been recently discovered in the respiratory specimens of children and HIV-positive patients. The etiological role of KI PyV in respiratory disease has not been proved yet, but as a member of the polyomavirus family, the virus has oncogenic potential and is probably involved in development of human disease, especially in individuals with immunodeficiency. The published prevalence of KI PyV among children with respiratory diseases ranges from 1 to 4.8%, but in HIV-positive patients it is much higher.The aim of the study was to evaluate the prevalence of KI PyV in Bulgarian children with respiratory diseases.Specimens were collected from 123 children at an age from 1 to 16 years divided in two groups: first group of 86 children with respiratory diseases; and a control group of 37 healthy children. Samples were tested using a nested polymerase chain reaction (PCR) method. All patients that were positive for KI PyV were also tested by ELISA for IgM antibodies against other ...