Let's talk about the H1N1 virus. I know you haven't heard enough about it on the TV and the radio and the internet and the newspaper and Twitter and Facebook. (Did I leave anybody out?)
First, go read what I did at Boing-Boing about cytokines and a cytokine storm.
Then read what Older Son has to say on the subject.
Also, that lady didn't make the point that for any bug, including this one, your probability of developing the infection absolutely depends on how much of it gets into your body. It also depends on how good your immune system is and how few of this organism are able to cause disease in a healthy person (the infectious dose). But you can't control either of those, and if they're constant the thing you can have some control over is how many of the things get into your system. That's why even a mask that doesn't stop all of the virus can be a good idea.
The other thing The Boy told us on the phone last night was that the difference betweeen cytokines and hormones was that the former were discovered/studied by microbiologists (I think) and the latter were discovered/studied by endocrinologists. They do essentially the same thing, enable communication between cells. That is of course a cynical oversimplification of the sort that always appeals to me, so you may take it with however much salt you deem appropriate.
And now you know lots about virii and cytokines and such.