In each of the four major pandemics since 1889, a spring wave of relatively mild illness was followed by a second wave, a few months later, of a much more virulent disease. This was true in 1889, 1957, 1968 and in the catastrophic flu outbreak of 1918, which sickened an estimated third of the world's population and killed, conservatively, 50 million people.
There is good news. The current swine flu does not have some of the genetic elements of more fatal flus, and our ability to spot and respond to outbreaks is much better than it was during any previous pandemic. But there is also worrying news. They have confirmed human to swine transmission in Canada, which means the flu may bounce back and forth and have additional opportunities to recombine. More importantly, this virus has a novel genetic makeup, so existing treatments may not work if it mutates into a more virulent form.
There is an additional factor to consider. We survive on resources that are provided to us on the tail-end of global, low-inventory, just-in-time, supply chain system. While this supply chain gives us access to a remarkable array of goods at low prices in good times, it is not clear how it would respond to the stress of a truly dangerous pandemic. My read is that any serious disruption would lead to wholesale breakdown. Your local grocers have sufficient inventory to feed the populace for about three days. The government certainly has more resources, but post-Katrina, I have a little confidence in the government responding well, especially when the significance of a virulent pandemic would dwarf Katrina.
In short, the odds are that this will not be a catastrophic flu pandemic, but on the other hand, if the virus happens to mutate to a truly virulent form, the consequences could be far worse that most people are predicting. The good people of flutrackers.com recommend you have sufficient foodstocks to last you three months in an emergency. It's an annoying expense, and odds are, you will be donating most of it to a food bank sometime down the road, but it's a matter of risk management.
Personally, I am building that inventory and hoping it all goes to waste.