OSHKOSH, Wis. (AP) -- Underneath Lake Winnebago's water is an invader.
Anglers fear the viral hemorrhagic septicemia virus in the Lake Winnebago chain could devastate Wisconsin's billion dollar-plus fishing industry.
Wildlife officials detected the virus in May.
The virus poses no threat to humans, but can cause many fish like trout and bass to bleed to death.
It already has spread through much of the Great Lakes.
Ohio officials estimate the virus killed hundreds of thousands of freshwater drum in Lake Erie last year.
The virus hasn't been detected in Lake Superior or the Mississippi River yet.
But it has appeared in inland waters in Michigan, New York and now Wisconsin.
No one knows for sure how much damage the virus could cause in smaller, inland waters.
But the Lake Winnebago system is a gateway to hundreds of miles of trout streams and lakes.
Some anglers fear Wisconsin's reputation as a national fishing destination could be in jeopardy.