One thing that works against the swine-flu is its short incubation period of only 1-3 days. In 1918 that would have protected the Icelanders, among others, but today with air-travel we are more at risk from these very virulent strains.
Yup. That is one thing. With the stunningly fast transport of both people and fresh goods it could mean that this one keeps "stabbing", but the better news is that it perhaps not turn into a medieval style plague.
By the way, when the Spanish flu was raging, it was just about the end ow WW1. In Europe, conditions were so and so, as well as the nutritional status.
Up here, there had been hard times for all (very cold winter and a naughty volcanic eruption on top of the WW1 effect on transport of goods), so when the flu hit, it was a soft spot. Many people died because they were not nursed, and entire families died, since all got sick, and nobody could stand in their legs properly enough to nurse the others.
One thing for concern though. The casualty rates were highest where least expected. You'd expect infants and the old, but in this case it was in the range of 20-40.
If this gets going around much, it is bad. Really bad.