This type of VHS isn’t a tape for your cassette player, but a fish disease that is rapidly spreading throughout the United States and the world. Scientifically known as Viral Hemorrhagic Septicemia, VHS was recently found in Lake Superior for the first time. The first Great Lake infection was found in 2003, and as of now every lake is infected. Large fish kills have been documented in lakes Ontario, Erie and Huron since 2005.
Worldwide, over 50 species of marine and freshwater fish carry the VHS virus. Because the virus normally can’t tolerate warmer waters— 59 degrees and up—scientists thought warm-water fish species were immune, but this has changed. Scientists now believe the virus is mutating into a new substrain that is infecting warm-water species, although as of yet no outbreaks have been reported in waters over 64 degrees.
The VHS virus affects fish differently worldwide. In Europe, for example, rainbow trout are highly susceptible, while North American rainbow trout seem to be immune. But overall, the list of infected species is growing and includes flounder, herring, salmon, whitefish, sea bass, cod, perch, crappie, bass, bluegill, and more.
The disease is highly contagious, and quarantines are the only effective way to control outbreaks. Unfortunately, oceans can’t be quarantined. No anti-viral agents or vaccines have yet been developed, and the outlook on stopping this disease is not promising. For now, scientists are concentrating on monitoring fish health and hatchery disinfection. Infected fish farms are being drained and treated while dry to kill the virus. But these methods are limited, and scientists are scrambling to find ways to better fight this disease as it continues to spread.
