A deadly fish virus suspected of killing thousands of fish in the Great Lakes basin appears to be spreading to new species, researchers say.

Since May, viral hemorrhagic septicemia is believed to have killed several thousand fish in Lake Ontario and the St. Lawrence River, said Paul Bowser, a professor of aquatic animal medicine at Cornell University in Ithaca, NY.

The virus doesn't pose a health risk to humans.

When it infects fish, it can cause fatal anemia and hemorrhaging in the gills and eyes, according to the World Organization for Animal Health's fact sheet on the disease.

The course of the disease is brief and mortality is high.

The virus was first detected in the northeastern U.S. in 2005 and in dead fish from the Bay of Quinte in eastern Ontario this spring.

The virus has now been found in 12 fish species in the Great Lakes, including chinook and coho salmon that are key to tourism in New York state.

Other infected species include:

• Smallmouth bass.
• Freshwater drum.
• Yellow perch.
• Northern pike.
• Yellow walleye.

Canadian scientists are watching for signs of infection in rainbow trout, the species most commonly farmed for human consumption in Ontario.

Researchers suspect fish can be infected and carry the disease without showing symptoms.

The disease can occur at any age, but younger fish seem to be most susceptible.

Infections are more likely when temperatures are between 4 C and 14 C, and outbreaks are more common in the spring as water temperatures change.

With files from the Canadian Press