NB: Val is very, very far from a medical expert. I've just been rereading The Great Influenza, about the flu epidemic of 1918, so mainly I'm drawing from that.
This H1N1 influenza is technically the same strain from 1918. BUT it is a much milder form of that virus. It never went away after that terrible outbreak, just mutated so as to be less deadly. Like the 1918 flu, though, when it kills, it most often kills otherwise healthy young adults, not the very young or very old as with most flu strains.
All influenza strains are endemic, meaning always present somewhere or other, even if only in birds or swine. Flu can be transmitted from birds to humans only in extreme cases of severe overexposure (poultry workers, for instance, as happened in Hong Kong) and those humans cannot in turn infect other humans. Domesticated pigs are sometimes the medium through which bird flus get into the human population, though: bird flus can infect pigs, and pigs can infect humans.
But yes, we have had in the past, and will have in the future, these waves of infection from influenza every so many years -- usually there's just enough time in between for people to forget how bad the previous one was, and make lots of people panic again, unfortunately.