Scientists in Winnipeg are toiling over two viruses that are giving experts in the flu world more than a few sleepless nights - the H5 and H7 avian influenza strains, considered the biggest threats to cause the next flu pandemic.

Researchers at Canada´s National Microbiology Laboratory are working with the viruses in a bid to help the scientific community crack the mysteries of their virulence, the director of the lab explains.

Dr. Frank Plummer says there´s another imperative driving the research, which involves making the precursor of a human vaccine - known as a viral seed or seed strain - for an H7 virus.

"The other major reason for doing it is building Canadian scientific capacity in this area so that we can respond better to the emergence of a pandemic flu," Plummer said in an interview from Winnipeg.

"I think that we should be an active participant in production of vaccine seed strains. We shouldn磘 be waiting for someone else to do it for us. And that´s what we磖e trying to do."

Influenza experts believe another pandemic is inevitable, perhaps even overdue. They have been quick to welcome Winnipeg into the small circle of laboratories doing the crucial work.

"We think there are too few people who work on the subject. So it´s really great that they are also embarking on this project," says Dr. Klaus Stohr, head of the World Health Organization´s global influenza program.

"We know so little. There is so much to do."

A top priority for the Winnipeg team is using viral samples collected during last spring´s devastating H7N3 avian influenza outbreak in B.C.´s Lower Mainland to produce a precursor vaccine.

Such work is vital, says Dr. Keiji Fukuda, a leading flu expert with the U.S. Centers for Disease Control in Atlanta.

"I think that one of the best things that we can do is to work on developing seed viruses for potential pandemic viruses and get as much experience as we can with developing them as quickly as possible."

"Anything that can reduce the time toward having vaccine available in that situation, given the unpredictableness of what might appear, is only going to help us."

H7 is one of two influenza subtypes - H5 is the other - for which it is particularly difficult to develop vaccines because they kill chicken embryos. Flu vaccines are grown in fertilized chicken eggs.

To get around that once-insurmountable hurdle, researchers now have at their disposal a technique called reverse genetics. In essence, it plucks the deadly bits out of the virus, allowing it to grow in eggs.

It is a technique the Winnipeg lab has used before, in developing a viral cousin of the 1918 Spanish flu virus. But that work was a collaboration with researchers from the University of Wisconsin. The Winnipeg team needs more experience doing such work on their own, Plummer says.