A postal worker holds up a leaflet giving information about swine flu in Cromarty, Scotland, on May 5, 2009. The government distributed leaflets to all U.K. households giving information about swine flu and advice on how to prevent its spread.

Photo Illustration by Jeff J. Mitchell/Getty Images

There comes a time of year when no place seems safe. You enter a crowded bus or subway car only to see runny noses and sallow, sickly complexions. You hear sniffles and sneezes in the grocery store and the gym. An entire day at work might be spent listening to a co-worker hack up his or her lung. And anywhere you might encounter children seems like a minefield; while these young minds soak up knowledge at school, their bodies attract all manner of germs. No doubt about it: Cold and flu season is a terrifying time.

However, we may soon long for the innocent, carefree days when the cold or flu was all we had to worry about. Just a year ago, pigs were more likely to be characters in children's books than to star in the punch lines of late night television shows. That was before the spring of 2009, when the first case of swine flu was documented in Mexico. Swine flu frenzy gripped the world, and sales of face masks and antibacterial hand lotions skyrocketed. Whispering the words "swine flu" on a plane might have been likened to yelling "fire!" in a crowded theater.

The 2009 virus circulating the world isn't strictly swine flu; rather, it's a mix of swine, avian and human influenza viruses that has never been seen before in humans. Public health organizations prefer names that feature some combination of H1N1, the year 2009 and type A influenza when referring to the disease, but the term "swine flu" remains lodged in the public's vernacular. Officials warn that we might be hearing more about it as the 2009 cold and flu season approaches.

In the upcoming months, we'll be dealt the double whammy of seasonal flu season and a potential second wave of swine flu. What's the difference between the two?