with an apparently well established marine reservoir in the Black Sea. To keep track of the distribution of different VHSV genotypes, a database called Fishpathogens.eu has been created to store data on different fish pathogens (including VHSV) and their sequences. Evolution This virus appears to have evolved in the Pacific Northwest of North America. It appears to have diverged into several strains ~300 years ago. Great Lakes Type IV-b The Type IV-b strain of VHSV has been spreading among freshwater fish in the Great Lakes region since at least 2003, resulting in some massive die-offs since 2005 of many species in the affected lakes. Originally found off the Atlantic coast of Canada, it was considered a low mortality marine strain. Its first detection in freshwater was in Lake Ontario in 2005, and then in an archived 2003 sample from Lake St. Clair. The isolate was named MI03GL and was sequenced for its entire genome. The North American genotype of the virus, in addition to moderate mortality to salmonid species, including various varieties of trout, is also proving virulent among a wide variety of warm-water species previously considered resistant to VHS. The Great Lakes region variant has killed lake trout, steelhead trout, chinook salmon, yellow perch, gobies, emerald shiners, muskies, whitefish, and walleye. While the European strain of VHSV is particularly deadly to rainbow trout, the Great Lakes region variant affects the species only mildly, as is typical with primarily marine genotypes. Great Lakes regional distribution An archived 2003 sample from Lake St. Clair of Great Lakes muskellunge is the earliest confirmed case of VHSV within the Great Lakes region. Lake St. Clair connects to Lake Erie through the Detroit River to the south, and to Lake Huron through the St. Clair River to the north. The sample was not tested for VHS until 2005, after the disease was detected in Lake Ontario. 2005 samples of Lake Ontario freshwater drum and Lake Huron lake whitefish were infected with VHS. Initially classified as an unknown rhabdovirus, the Lake Ontario sample was confirmed to be VHSV in 2006, while the Lake Huron sample was confirmed to be VHSV in 2007. 2006 saw mass die-offs from VHS in Lake Erie, the St. Clair River, the Detroit River, and the St. Lawrence River, which connects the Great Lakes to the Atlantic Ocean. VHS was further detected in the Niagara River, which connects Lake Erie to