Exploiting Viral DNA Genomes to Explore the Dispersal History of African Swine Fever Genotype II Lineages in Europe.

African swine fever virus (ASFV) is a highly virulent DNA virus that causes African swine fever, a severe hemorrhagic disease affecting domestic and wild pigs, leading to significant animal health burdens and economic losses. Initially limited to the sub-Saharan African region, ASFV genotype II has spread globally and is now a major concern in Africa, Europe, Asia, the Pacific and, more recently, the Caribbean. In this study, we performed phylogenetic and phylogeographic analyses using newly sequenced ASFV genomes from Lithuania, combined with previously available complete genomes, to investigate the spatiotemporal dispersal dynamics of ASFV genotype II in Europe. Our analysis suggests that ASFV genotype II has not been recently imported to Europe from other regions; instead, the spread is largely driven by long-distance dispersal, followed by regional (within-country) circulation. The estimated dispersal metrics suggest that ASFV has a slower dispersion capacity compared to other pig-transmitted viruses and is associated with a notable degree of spatial structure. Despite these findings, significant uncertainty remains regarding certain ancestral locations, highlighting challenges related to applying phylodynamic methods to DNA viruses with low genetic variability. Nevertheless, in our study, we managed to implement a phylogeographic framework to investigate major patterns of ASFV dispersion in Europe and the contribution of international importations in the establishment of regional transmission chains. This framework could be further expanded as more genomes become available. Our study emphasizes the need for increased genomic surveillance to enlarge the ASFV genome database to support outbreak control.