Abstract
Polyomavirus (PyV) was discovered by accident in 1950 in the course of describing an infectious factor causing multiple tumours in rodents. The term is derived from two Greek words: poly (many) and oma (tumour). At present the family of human polyomaviruses (HPyV) consists of 10 members. One of the first members was BK virus, isolated in 1971 from the urine of a renal transplant patient. Serological examinations have shown that due to its ability to cause latent infection, about 90% of the general population can have specific antibodies attesting infection. In the case of infected persons with normal immunity, this virus is not dangerous. In the impaired immunity, however, loss of immunity results in virus reactivation and development of many life-threatening illnesses. Serological examinations have also reveal that BK polyomavirus considerably affects the development of cancers in humans. Hence, in 2012 a group of 26 researchers from 11 countries associated with the International Agency for Research on Cancer (a part of the World Health Organisation) classified BK polyomavirus within group 2B - “potentially carcinogenic to humans”