Katie Couric's Notebook: Immune System

It's a natural tendency.

Someone nearby sneezes or blows his or her nose ... and we run for cover.

Whatever he has ... we don't want it.

But it turns out that just seeing someone suffering like that ... might actually be good for our health.

Scientists from the University of British Columbia sat down with several groups of people. Each was shown a series of photographs. Some had to look at pictures of people who were obviously ill ... coughing or with a runny nose or rash.

The researchers then compared before and after blood samples and found that looking at all those sick people made participants' immune systems kick into over-drive ... protecting them from what their bodies saw as an imminent threat.

It's a reminder just how amazing the human body is. Even when we can't play defense as someone sneezes our way ... Mother Nature may somehow be there quietly saying "God bless you."

That's a page from my notebook.

I'm Katie Couric, CBS News.