During cold and flu season — or any season, really — germs like to hitch a ride on hands, backpacks and shoes. Their destination? Your house.

Although many of these freeloaders are harmless, some bacteria that get inside homes are pathogens like E. coli or other germs that cause disease. You can't keep every potential intruder out, but there are simple precautions you can take to protect yourself, according to microbiologist Joe Rubino, a member of the Global Hygiene Council who works for the England-based hygiene company Reckitt Benckiser.

Related: E. coli 101: How to Recognize E. Coli Symptoms, and How to Avoid Them

Wash those hands. If you’ve been out and about, he says, your hands have undoubtedly picked up germs from things you’ve touched, from the keypad at the ATM to the handle on the grocery cart. To keep those germs from settling in to your home, head straight from the front door to the sink, advises Rubino. “Anytime you come home from work or shopping, wash your hands,” he says.

Kick off your shoes. “I’m a big advocate of leaving shoes at the front door,” Rubino says. In unpublished research conducted in 2008, researchers at the University of Arizona found the outside surfaces of shoes harbored an average of 421,000 units of bacteria. (Each “unit” contains enough germs to start another colony.)

The germs included Klebsiella bacteria (which can cause blood stream infections and pneumonia) and Serratia ficaria (a rare cause of wound and lung infections). Ninety-six percent of the shoes carried E. coli, the intestinal germ that, if ingested, can cause infections that are unpleasant and sometimes serious or even life-threatening, according to the Mayo Clinic.

Be grocery smart. Some unpleasant bugs like to live on raw meat, poultry and fish. That means the package you bring home from the store could be a Trojan horse of germs. A study by Consumer Reports found 43 percent of retail raw chicken products contained campylobacter bacteria, while 11 percent contained salmonella, both of which cause food poisoning.

What's more, a 2014 study by the Department of Agriculture found consumers tend to spread raw poultry juices at home after shopping by setting raw meat on the counter (33 percent), the kitchen table (4 percent) and the sink (4 percent). And 35 percent put meat in the fridge without putting it in a bag.

Related: 9 Surprising Places Salmonella Bacteria Lurk

Never buy packaged proteins that are drippy or sticky. At checkout, Rubino advises putting meat products in a separate bag from other items. Don’t let groceries sit for long in the car; put them away promptly when you get home. Double-wrap meat, poultry and fish before putting it in the fridge or freezer. Rubino notes people are careful about raw meat when they’re cooking, “but they’re not thinking about it as much when they’re bringing it home or putting it away.”

Hang up diaper bags, backpacks and purses. A study by microbiologist Chuck Gerba, PhdD, of the University of Arizona, found a third of women’s purses had fecal bacteria on the bottom. One purse evaluated was teeming with 6.7 million bacteria. Others were 100 times more contaminated than the average toilet seat. Gerba advises never putting purses or backpacks on the floor in a restroom (or anywhere). Instead, hang them on doors or chairs. At home, keep purses and backpacks off kitchen counters.

Wash clothes frequently. Outside germs can latch onto clothing and hitch a ride into your house. “If I’m out in New York City, sitting on a subway seat where thousands of people have been before, I’m going to want to wash my clothes when I come home,” Rubino says.

Brand-new clothes may not be all that clean either, especially those that might have been returned, according to a 2010 ABC investigation. Working with investigators, Philip Tierno, PhD, of the New York University School of Medicine, found some new clothes — including a silk blouse — were “grossly contaminated” with fecal and vaginal bacteria. Others carried norovirus and staph germs. Tierno suggests washing new clothes before wearing them.

Related: Norovirus: Coming to a Meal or Surface Near You?

Don’t let dog or cat poop pile up. If your dog relieves himself in the yard, clean it up at least once a week, advises Wisconsin veterinarian Race Foster, DVM, on his website. You'll lower the chances the dog or anyone else will track in waste and the infectious organisms that go with it, including E. coli, hookworms and roundworms. Likewise, he advises cat owners to scoop the litter box at least once a day and completely replace the littler at least every week. As an extra precaution, wipe down pets’ paws after they come inside.

Chris Woolston, M.S. is a freelance writer and editor who specializes in science, health and travel. A reformed biologist, Woolston says, he studied algae and nitrogen dynamics in Antarctic lakes before the Science Writing Program propelled him out of the lab. He is a contributing editor at Nature.com, a former staff writer for Time Inc.’s Hippocrates magazine, and co-author of Generation Extra Large (Perseus). He lives in Billings, Mt., with his wife – novelist Blythe Woolston – and their two children.