Laura Stremick-Thompson, a fisheries biologist at the state Department of Natural Resources, tells The Janesville Gazette the die-off started at the Rock River in July, reached Lake Koshkonong last week and will probably arrive in Janesville and Beloit in the next few weeks.
The biologist says local residents have reported hundreds of dead fish downstream of Lake Koshkonong and upstream of the Indianford Dam. One man says he has picked up about 30 dead carp along the Lake Koshkonong shoreline.
Stremick-Thompson says the koi herpes virus affects carp like Ebola affects humans. She says the mortality rate of the virus can reach up to 80 percent.