Bullhead City, Arizona - Biologists have determined that a carp die-off in Lake Mohave is being caused by a virus.

Several thousand dead carp have washed up on the shore of the reservoir along the Colorado River in recent weeks. Arizona Game and Fish Department spokesman Zen Mocarski says it appears the Koi herpes virus has now spread downriver and is killing carp in Lake Havasu.

The virus can affect goldfish, koi and carp, but is not dangerous to humans.

The virus affects gill function, which can lead to suffocation or secondary infections. Mocarski says the ill fish aren't dangerous but it is best to avoid them.