Feb. 20, 2011 -- An average adult can touch as many as 30 objects within a minute, including germ-harboring, high-traffic surfaces such as light switches, doorknobs, phone receivers, and remote controls. At home, you do all that you can to keep the germs at bay. But what happens when you step out the door to go to dinner, do some grocery shopping, or visit the doctor's office? Know where germs are most likely to lurk, as you'll find out here.

Restaurant menus

Have you ever seen anyone wash off a menu? Probably not. A recent study in the Journal of Medical Virology reported that cold and flu viruses can survive for 18 hours on hard surfaces. If it's a popular restaurant, hundreds of people could be handling the menus--and passing their germs on to you. Never let a menu touch your plate or silverware, and wash your hands after you place your order.

Lemon wedges

According to a 2007 study in the Journal of Environmental Health, nearly 70% of the lemon wedges perched on the rims of restaurant glasses contain disease-causing microbes. When the researchers ordered drinks at 21 different restaurants, they found 25 different microorganisms lingering on the 76 lemons that they secured, including E. coli and other fecal bacteria. Tell your server that you'd prefer your beverage sans fruit. Why risk it?

Condiment dispensers

It's the rare eatery that regularly bleaches its condiment containers. And the reality is that many people don't wash their hands before eating, says Kelly Reynolds, PhD. So while you may be diligent, the guy who poured the ketchup before you may not have been, which means his germs are now on your fries. Squirt hand sanitizer on the outside of the condiment bottle or use a disinfectant wipe before you grab it. Holding the bottle with a napkin won't help; napkins are porous, so microorganisms can pass right through, Reynolds says.

Restroom door handles

Don't think you can escape the restroom without touching the door handle? Palm a spare paper towel after you wash up and use it to grasp the handle. Yes, other patrons may think you're a germ-phobe--but you'll never see them again, and you're the one who won't get sick.

Soap dispensers

Grocery carts

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Airplane bathrooms

Doctor's office

1. Take your own books and magazines (and kid's toys, if you have your children or grandchildren with you).

2. Also pack your own tissues and hand sanitizers, which should be at least 60% alcohol content.

3. In the waiting room, leave at least two chairs between you and the other patients to reduce your chances of picking up their bugs. Germ droplets from coughing and sneezing can travel about 3 feet before falling to the floor.

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More from Prevention:

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12 Health Lessons Straight From The Lab

10 Worst Germ Hot Spot