A lot of you have had it by now, or are having it or are about to be exposed. This year's flu is called "H3N2" and this week it's doing big business in about 47 states, Chicago and New York. If you've had a flu shot and if you wash your hands several times a day for 20 seconds, (which is the time it takes to hum "Happy Birthday to You" two times through) you might reduce your odds of getting sick.

But your biggest ally is your immune system. It's hard, during flu season, to avoid inhaling a virus or two (or three, or 10,000), but that doesn't mean they're going to take you over. You have an army of defenders in you, ready to take them on.

Here's what the battle looks like, deep down in your cells. This is the happy version -- when you win.

The last time I posted this video, I added this caveat, which I want to add again: Your immune system includes mucus and other body fluids that trap the viruses and destroy them; You cough and sneeze a lot, which hurls them back out into the air where they usually die. Plus lots of viruses are dweebs. They don't work that well. Some don't have the right "keys" to invade healthy cells so they can't spread the infection. That is why most of the time, after a struggle (when you get a fever and need to lie down), your immune system rebounds, and, in time, so do you.