Emergence and resurgence of the viral hemorrhagic septicemia virus (Novirhabdovirus, Rhabdoviridae, Mononegavirales)

Viral hemorrhagic septicemia virus (VHSV) is one of the most serious pathogens of finfish worldwide in terms of its wide host-range, pathogenicity, disease course, and mortality rates. The disease was first documented in the 1930s in Europe in association with heavy losses in rainbow. Data collected over 50 years show that VHSV is a virus of marine origin: its ability to alternate between marine and freshwater environments remains an enigma which requires further investigation. In 2003, VHSV invaded the Laurentian Great Lakes basin causing devastating losses. VHSV is believed to have negative impacts on a number of important Atlantic, Pacific, and Great Lakes fish species. Phylogenetic analysis has offered clues into the geographic and host range of the virus, but sporadic outbreaks of the disease in uncommon locations have imparted unforeseen challenges in delineating the virus’ regional distribution.