Avian flu is evolving. How worried should the world be?

It used to be a threat almost exclusively to the poultry industry. But the current strain of H5N1 avian flu has spent the past year infecting millions of wild birds, thousands of mammals, and even humans. To experts who track the disease, it's clear something is up. But we're not yet sure what comes from it.

The virus could become more contagious in mammals, but less harmful. It could remain difficult to transmit widely outside of bird populations. It could, theoretically, go away gradually. But it also might not. There is pandemic potential here and the questions on experts' minds is if we are sleepwalking towards another disaster...

GUEST: Dr. Shayan Sharif, acting dean of the Ontario Veterinary College, professor of pathobiology