Viruses of the genus Pestivirus, family Flaviviridae, are believed to be among the main factors causing economic losses in cattle and pig breeding. Their genomes, consisting of single-stranded RNA with positive polarity and a length of approximately 12.3 kb, have one open reading frame that encodes from 11 to 12 proteins. The virion is surrounded by a lipid membrane. According to the official classification, the genus Pestivirus includes four species: bovine viral diarrhea virus-1 (BVDV-1), bovine viral diarrhea virus-2 (BVDV-2), classical swine fever virus (CSFV) and border disease virus (BDV). To date, several genetically related viruses have been identified, but not yet included in the official classification. They include: giraffe pestivirus isolated from an animal with symptoms of mucosal disease and from cell cultures originating from Kenya, Pronghorn virus from an antelope, HoBi-like viruses detected for the first time in fetal bovine serum and Bungowannah virus causing losses in the Australian domestic pig population. It is suspected that new strains detected in Turkish goat and sheep herds and in Tunisian sheep pox vaccines also belong to pestiviruses. Next-generation sequencing has made it possible to identify another atypical pestivirus of pigs, as well as to discover strains infecting other animals beyond the order of Artiodactyla, such as rats or bats. New emerging strains may pose a threat to the livestock industry.