TORONTO — Thanks to the threat of H5N1 avian influenza, tons of work was done in the past five years or so to prepare for a flu pandemic.

But in the end that dangerous virus, more commonly known as bird flu, didn't spark the first pandemic in four decades. Instead, a hybrid of two viruses that have been circulating in pig populations merged and gave rise to a new virus - swine flu - that made the species jump.

Pandemic H1N1 has been a relief, causing far fewer deaths than what would be expected if H5N1 caused a pandemic. Still, this relatively mild virus has taught public health some key lessons - something experts see as a welcome upside to an unwelcome outbreak.

Here are some thoughts on some of those lessons:

Antiviral drugs: The two key drugs, Tamiflu and Relenza, hadn't been widely used (except in Japan) before this pandemic.

Doctors treating the severely ill have relied heavily on them and the emerging evidence suggests they make a difference in the ICU. As well, they've been used to try to prevent serious illness in people at high risk of becoming gravely ill with this flu.

"We've learned a lot and we can use that going forward," says Dr. Nancy Cox, head of the influenza division at the U.S. Centers for Disease Control. "And so they are likely to become a more integral part of influenza prevention and control in the long run."

Vaccine production shortcomings: Experts have known for years that the world's combined flu vaccine production capacity would be inadequate in a pandemic. Still, it was thought the problem would be that affluent countries would have vaccine and developing countries would not.

Instead, production problems meant no one - with the possible exception of Australia - had enough vaccine in time to have a big impact on the first or second waves of illness. Dr. Michael Osterholm says this outbreak should serve as a turning point on this issue.

"We finally have a sharpened view of what this vaccine is all about and everyone agrees ... that it's simply inadequate," says Osterholm, director of the University of Minnesota's Center for Infectious Diseases Research and Policy.

"That, I think, could be a sea change right there. If we could fundamentally improve on influenza vaccine... we could fundamentally change the impact of this disease on society."

Influenza surveillance: The need to track the movement of the pandemic virus meant laboratories in the far reaches of the world have been equipped with flu diagnostics.

Places that weren't using PCR - polymerase chain reaction - testing are now doing so, says Cox, who notes that means there will be more laboratories in the hunt for the next new flu virus.

"So we're going to have a better early warning system globally."