Viral Hemorrhagic Septicemia Virus (VHSV-IVb)

Scientific Name: Novirhabdovirus sp. genotype IV sublineage b

Photo courtesy of P. Bowser, Cornell UniversityCopyright Info

Identification: Viral Hemorrhagic Septicemia (VHS) is caused by a virus that infects fish in both marine and freshwater environments. Infection signs differ depending on the course of the disease. Some infected fish show no symptoms at all. Others may become hyperactive and display nervous symptoms, such as twisting of the body and erratic swimming. In its most severe form, fish become lethargic and dark, with bulging eyes as well as liver and kidney abnormalities. They also have bleeding in their eyes, skin, gills, fin bases, skeletal muscles, and internal organs. This form of the disease almost always kills the infected fish. In less severe infections, the death rate is low. Survivors may show no outward symptoms, but are capable of carrying and spreading the virus for the rest of their lives.

Size: Viruses are microscopic.

Native Range: VHS is native to eastern and western Europe, Japan, the Pacific Coast (from California to Alaska), and North America’s Atlantic Coast.

Map Key
This map only depicts Great Lakes introductions.


Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Novirhabdovirus sp. genotype IV sublineage b are found here.

State/ProvinceYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
Illinois200820081Lake Michigan
Michigan1999201112Boardman-Charlevoix; Cheboygan; Dead-Kelsey; Detroit; Huron; Lake Erie; Lake Huron; Lake Michigan; Lake St. Clair; Lake Superior; Lone Lake-Ocqueoc; Tittabawassee
Minnesota201020101St. Louis
New York1999201511Chautauqua-Conneaut; Headwaters St. Lawrence River; Irondequoit-Ninemile; Lake Erie; Lake Ontario; Lower Genesee; Niagara; Oak Orchard-Twelvemile; Oswego; Salmon-Sandy; Seneca
Ohio199920101Lake Erie
Wisconsin200720114Lake Michigan; Lake Superior; Lake Winnebago; St. Louis

Table last updated 5/25/2018

† Populations may not be currently present.

* HUCs are not listed for areas where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).

Means of Introduction: It is unknown how VHS was initially introduced to the Great Lakes–St. Lawrence River system. Genetic evidence suggests that the virus came from North America’s Atlantic Coast, and it was possibly transported in water from ships or by migrations of infected fish. Aquaculture, waterfowl, and bait transport have also been linked to the virus’ spread. It appears VHS becomes widespread once it is established in a region. It is also capable of persisting in fish that show no symptoms of infection.

Status: This virus has been present in the Great Lakes since at least 2003. It has been found in dead or diseased fish in all of the Great Lakes and several inland lakes in Ohio, New York, Michigan, and Wisconsin.

Remarks: A United States federal order aims to prevent the spread of the virus into aquaculture facilities by restricting the interstate movement and importation of live VHS-susceptible fish. There is no indication that this disease is a threat to human health.

Author: Illinois-Indiana Sea Grant

Contributing Agencies:
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Revision Date: 4/24/2012

Citation for this information:
Illinois-Indiana Sea Grant, 2019, Viral Hemorrhagic Septicemia Virus (VHSV-IVb): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI,, Revision Date: 4/24/2012, Access Date: 9/19/2019

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.