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.

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, 2017, 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: 10/21/2017

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.