Pestiviruses are highly variable RNA viruses within the Flaviviridae family causing economically relevant diseases of different kinds of livestock. A newly identified Pestivirus, the atypical porcine pestivirus (APPV), was identified in the USA in 2015. Since then, different APPV outbreaks were detected in several European countries, in America, and in Asia as well. Studies have shown that pregnant sows inoculated with APPV positive blood-or tissue-suspension are farrowing piglets affected by A-II type congenital tremor (CT). CT is characterized by a typical shaking of the head and the limbs of newborn piglets and is often complicated with splayed legs. Whereas the shaking itself is not the direct cause of death, it can prevent the piglets from proper nutrition, resulting in a decrease of growth rate and even death by starvation. Recently, numerous pigs of different Hungarian herds were showing signs of CT and therefore they have been investigated for the presence of APPV by our research group. The aim of my research was to detect the virus in Hungarian swine herds, to characterize the strains and compare them to each other and to previously published sequences that can help in cognition of their origin, spread, and genome evolution. The second objective was to localize and visualize the virus in various tissue samples. To do so, various tissue samples were obtained from four affected piglets, that were necropsied in 2017. One part of the samples were kept in –80 ºC for PCR-based virus detection, the other part was fixed in formalin and embedded in paraffin (FFPE). We isolated RNA from the frozen samples and detected the virus by conventional RT-PCR. We performed a novel RNA in situ hybridization method (RNAscope) on slides prepared from the FFPE samples to show the tissue localization of the virus. Based on recent scientific studies and the results of our research group, APPV is mostly localized in the inner granular layer of the cerebellum, which is reported to be responsible for the clinical signs, and also in the ependymal and subependymal cells of the cerebrum.