Some context to the swine flu story may explain why people who work in public health are worrying so much about what flu can do.
This particular example is extreme, but the time it occurred is interesting because it was during a period of great stress for humanity (the Great War). Perhaps collective, or group resistance to a virus is lower than it might usually be at moments like those we are in now.
There are some details on what is being planned in the UK here – just in case.