Reemergence of arctic-like rabies virus in a rabies-free area in the Amur river basin

Background: A descriptive epidemiological study of the rabies outbreak in the Amur Region of Russia (ARR), which remained rabies-free from 1972 to 2017, was carried out. During 2018-2022, 49 animal rabies cases and one human rabies death were documented in the ARR. This study aimed to detect possible ways of incursion and features of the spatial spread of rabies virus (RABV) in ARR, which was considered rabies-free for 45 years. Methods: After the beginning of the outbreak, 1,450 animal brain samples were tested using a direct fluorescent antibody test. Genetic analysis of RABV isolates was carried out (n = 9). GIS was used to analyze the spatial spread of rabies in ARR and adjacent territories. Results: Rabies has been confirmed in red foxes (Vulpes vulpes ) - 38.8%, raccoon dogs (Nyctereutes procyonoides ) - 10.2%, wolves (Canis lupus ) - 14.3%, dogs - 18.4% and farm animals - 18.3% (n = 49). The first cases were detected south of the ARR, 30 km from the state border between Russia and China. In 2018-2022, the RABV spread within the forest-steppe landscapes of the Zeya-Bureya Plain northwesterly; the maximum distance from the first recorded event was 192.4 km (Me = 77.6). According to a phylogenetic analysis, the isolates from ARR belonged to the Acrtic-like-2 RABV lineage and showed the maximum similarity to the isolates recovered in the province of Heilongjiang (China, 2011, 2018) and the Jewish Autonomous Region (Russia, 1980). Conclusion: Rabies was most likely introduced by wild carnivores from the adjacent territories of Russia or China, located downstream of the Amur River.