The average American goes to the supermarket twice a week and is exposed to bacteria from a variety of sources — from the grocery cart handle to the melons in the produce aisle. Even when your groceries are safely at home, you still have to contend with food-borne illnesses. More than 70 million people get sick from food-borne illnesses in the U.S. each year, and roughly 5,000 of them die as a result of it, according to the Centers for Disease Control and Prevention. And if you’re pregnant, diabetic, HIV-positive or over the age of 65, then it’s even more risky for you to sample the grocery store's cheese display or skip the produce bags.

Luckily, there are several precautions you can take — both at the grocery store and at home — to help keep you and your family safe.

Sanitize Your Shopping Cart

In a 2007 study at the University of Arizona, researchers found that two-thirds of the grocery carts they swabbed were contaminated with fecal bacteria. In fact, the bacterial counts exceeded those of the average public restroom. Plus, indirect contact with sick people — such as touching the same cart someone with a cold used earlier — is an easy way to get sick.

Some supermarkets put their carts through a "car wash" of disinfectant mist, but these stores are few. However, most grocery stores now offer sanitary wipes so shoppers can wipe down carts’ handles. If your local store doesn’t, bring your own or be sure to wash your hands after touching a cart. You can also purchase shopping cart handle covers like this one or even make a handle cover yourself.

Wash Your Reusable Bags

You’re doing an eco-friendly thing by bringing those reusable bags to the store — just make sure you wash them. A joint study by the University of Arizona and Loma University in California found that these bags can be a breeding ground for germs and food-borne bacteria. Researchers randomly tested reusable bags in three cities and found that most were home to high levels of bacteria, and E. coli was detected in half of the bags sampled.

Don’t let this scare you into going back to disposable plastic bags though — just throw your reusable bags in the wash now and then and you can be both green and clean.

Skip the Free Samples

The deli samples or bowl of dip may look tempting, but they could also be a home to all kinds of bacteria. In fact, a 2010 E. coli outbreak was linked to cheese samples at Costco. Walk past those free samples in these situations.

The food looks old: If the fruit looks dry or the cheese is sweating, it's probably been sitting out a while. You don't want to sample any foods that have been sitting out for more than two hours.

Communal trays: A sampling station should have individual portions, toothpicks, spoons, or forks. Avoid any bowls or platters where people are taking food with their bare hands.

There's no staff person: If there's no one nearby, you don't know how long the food has been sitting out or how it was handled.

Poor food preparation: If an employee is cooking food samples, pay attention to how the food is prepared. Are there separate knives and cutting boards for meat and vegetables? Are they using a food thermometer?

You haven't washed your hands: If you're shopping, you've probably touched shopping carts and food products, which have germs of their own.

Select Produce Carefully

Fresh fruits and vegetables are some of the healthiest foods we can eat, but they, too, can be covered in germs. Everyone touches and squeezes the produce, but not everyone washes their hands — a study by the American Society for Microbiology found that one-third of men didn’t wash their hands after using the restroom and 12 percent of women didn’t. Plus, produce has often been sitting in fertilizer and manure and on delivery trucks and store floors. While recently sprayed fruits and vegetables might look fresh, that moist environment is a breeding ground for germs, and most store systems recycle that water so it’s often full of bacteria.

When purchasing fruits like strawberries and grapes, look for cotton-like substances that could indicate spiders have been on them, and fuzz in the navel of an apple can mean it’s been stored too long. Studies have found that bruises and tears on fruit and vegetable skin are entryways for bacteria, so carefully check your produce before putting it in your cart.

And remember to wash your produce under free-flowing water before eating it — even if it says it's prewashed.

Watch Where You Place Your Groceries — and Your Kids

Don't put perishables in the seat compartment because children often sit there, making the area a breeding ground for germs. And you might want to think twice before placing your child in that seat. A 2006 CDC study of 442 infected infants in eight states found that riding in shopping carts next to meat was one of the biggest risk factors for Salmonella infections.

Check the Dates

Before purchasing an item — especially meat and dairy — check its expiration date to make sure the product is still safe to consume. “Sell-by” and “use-by” dates can be confusing, but they’re essentially quality dates that are based on consumer research of when people notice a decline in freshness. According to the FDA, the “sell-by” date tells the store how long to display a product, the “best if used by” date tells the consumer when the flavor is best, and the “use-by” date is the last date recommended to use the product while it’s at peak quality.

Typically, food quality is good for seven to 10 days from the time of packaging, such as with dairy products. However, for meat it’s usually about three days.

Select Prepared Foods Carefully

If you’re purchasing cold food, such as chopped melon or prepackaged lettuce, it should be maintained at 41 or degrees or below. Most refrigerated shelves have a thermometer attached at the top — if you don’t see one, ask a produce worker to check the temperature. Hot prepared foods should also be stored at the right temperature. Pick the package at the bottom of the pile to find the hottest one.

Cover All Your Food

Place all your produce and raw foods in bags — if you want to go green, pick up some reusable produce bags — because checkout counters’ conveyor builts are covered in germs. When Connie Morbach, a microbiologist with Sanit Air, a company that specializes in testing air in commercial properties, swabbed a supermarket conveyor belt, she found “organisms that are typically associated with open wounds that could cause infections.”

Also on MNN: How to avoid germs in public restrooms

Click for photo credits

Photo (grocery cart): Polycart/Flickr

Photo (reusable bags): McIninch/iStockphoto

Photo (cheese samples): Infrogmation/Flickr

Photo (produce aisle): Jellaluna/Flickr

Photo (expiration date): MNN

Photo (checkout): Chip Somodevilla/Getty Images