Hand-washing seems pretty simple, but a recent study shows that 97% of the time, we're still doing it wrong -- which can lead to contamination of food and surfaces and result in foodborne illness.

The study from the US Department of Agriculture shows most consumers failed to wash their hands and rub with soap for 20 seconds. That's the amount of time recommended by the Centers for Disease Control and Prevention, which says that washing for shorter periods means fewer germs are removed.

"Numerous" study participants also didn't dry their hands with a clean towel.

The study involved 383 people in six test kitchen facilities in the metro Raleigh-Durham area of North Carolina and in rural Smithfield, North Carolina, the USDA said.

Poor hand-washing practices led to cross-contamination, the study found. About half the time, participants spread bacteria to spice containers while preparing burgers, and 11% of the time, they spread bacteria to refrigerator handles.

"You can't see, smell or feel bacteria," said Carmen Rottenberg, acting deputy undersecretary for food safety at the USDA. "By simply washing your hands properly, you can protect your family and prevent that bacteria from contaminating your food and key areas in your kitchen."

The results from the USDA's study indicate our hand-washing habits may be getting worse. A study done in 2013 by Michigan State University found only 5% of people washed their hands correctly.

So what's the right way to wash hands? The CDC has some tips, starting with an obvious step: wetting hands with clean, running water.

Step 2: After wetting hands with water, turn off the tap and apply soap.
Step 3: Lather hands by rubbing them together with the soap. Be sure to lather the backs of hands, between fingers, and under fingernails.
Step 4: Scrub hands for at least 20 seconds. (Sing the alphabet song once or "Happy Birthday" twice.)
Step 5: Rinse hands well under clean, running water.
Step 6: Dry hands with a clean towel or air dry them.

A separate study released this month found 49 of 100 towels tested showed growth of bacteria normally found in or on the human body. That included E. coli and Staphylococcus aureus, often referred to as "staph."

The bacteria were more likely to be found on wet towels, and towels used for more than one purpose, such as wiping counter tops and utensils and drying hands, according to the study, conducted by researchers from the University of Mauritius.