Viral Hemorrhagic Septicemia (VHS) is a deadly virus that is threatening Wisconsin's fish. So far the disease has only been found in Wisconsin in the Winnebago system, the Bay of Green Bay and Lake Michigan. View a map of locations tested for VHS (PDF).
VHS was diagnosed for the first time ever in the Great Lakes in 2005 and 2006 when thousands of muskies, walleye, lake whitefish, freshwater drum, yellow perch, gizzard shad, redhorse, and round gobies died. Many other species of fish were diseased but did not die in large numbers.
VHS is NOT a threat to people who handle infected fish or want to eat their catch. It is a threat to the more than 25 fish species it can kill. This is the first time a virus has affected so many fish species from so many fish families.
The virus grows best in fish when the water temperature is 37 to 54 degrees Fahrenheit. Most infected fish will die when water temperatures are 37 to 40 degrees Fahrenheit. Stress is an important factor in VHS outbreaks. Stressors include spawning hormones, poor water quality, lack of food, or excessive handling of fish.
How do you know if your fish has VHS? Symptoms include bleeding, bulging eyes, unusual behavior, bloated abdomen, and rapid onset of death. But these symptoms could apply to many different fish diseases, so VHS can only be confirmed by lab tests. If you catch a diseased fish or observe a fish kill, contact your local WDNR fisheries biologist.
Additionally, some infected fish may not show any signs of the disease and transporting these fish to new locations could spread VHS to new waters. Infected fish carry the virus and shed it in their urine and reproductive fluids. The virus can survive in water for two weeks or more. Fish can even be infected if they eat an infected fish. Fish that survive the infection will develop antibodies to the virus, but the concentration of antibodies in the fish will drop over time and the fish may start shedding the virus again.
Fish shedding the virus through its fluids is the reason it is so very important not to move water from one water body to another. You cannot see if the water has been contaminated with the VHS virus. Wisconsin has adopted some very stringent rules and regulations to prevent the spread of VHS. The fines can be quite substantial, too. The complete set of laws- with a number of exceptions concerning bait- are best reviewed on the WDNR website. The WDNR updates this information often, so if you have questions, visit their site.
To simplify the laws concerning the prevention of spreading VHS, you must drain all water from boats, containers and fishing equipment when leaving any state waters, banks or shores, or entering Wisconsin over land. This does not apply to any drinking water or up to 2 gallons of water being used to hold minnows that can be legally transported. You may not transport any live fish or live fish eggs away from any state waters. There is an exception for minnows obtained from a Wisconsin bait dealer. These minnows may be transported away live and used again on the same water, or on any other waters if no lake or river water, or other fish were added to their container. Visit the WDNR website for additional information or regulations to prevent the spread of VHS.