(CNN) 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.