The Centers for Disease Control and Prevention has come out with a startling report. After scouring more than 10 years’ worth of data about foodborne illness outbreaks, researchers said that norovirus—the awful stomach bug that causes vomiting and diarrhea and that led to so many hospitalizations this winter—is responsible for more illness, by far, than any other pathogen (disease-causing agent).

And about half of foodborne illnesses originate from foods that we usually (and rightly) think of as healthful—specifically, from fresh fruits and vegetables!

You’re probably surprised, because people generally regard poultry and meat as the most likely sources of food poisoning. And those foods can indeed make you very sick if they carry salmonella or some other pathogen. But clearly, contaminated produce is a problem, too—especially since produce often is eaten raw and so the germs aren’t killed during cooking.

A recent study demonstrated an often-overlooked way in which norovirus and another scary virus are transmitted in the kitchen…and what you can do to stay safe.


For the study, researchers first disinfected various fresh fruits and vegetables—cantaloupe, honeydew, strawberries, carrots, cucumber, tomatoes—to get rid of any germs already present. Then they intentionally contaminated the produce with either norovirus or hepatitis A, a virus that causes potentially deadly liver infection. Both of these pathogens are commonly spread through food.

Next the researchers cut the contaminated produce with clean knives of various types (serrated, plain edge, sharp, dull) or shredded it with a grater to determine whether the viruses would be transferred to the cutting utensils.

Icky discovery: More than half of the previously clean utensils became contaminated after slicing through the contaminated produce.

Interestingly, not all foods were equally likely to transfer each virus. For instance, knives that cut honeydew wound up with the smallest concentration of norovirus but high concentrations of hepatitis A…while knives that cut cucumbers ended up with little hepatitis A but lots of norovirus. And the grater, which was used on carrots, picked up the most norovirus of all the utensils but showed below-average amounts of hepatitis A. Explanation: Differences in the structure of the two viruses and in the surfaces of the foods may affect how easily a particular pathogen is spread.

Even ickier: For the next part of the experiment, researchers took those same contaminated knives and grater and—without washing them—cut up produce that was not already contaminated. They wanted to see whether the now-dirty utensils would cross-contaminate the clean produce. And did it ever…for up to seven subsequent uses of the utensil!

By the way, it didn’t matter whether a knife was plain-edged, serrated, sharp or dull. All that mattered was that it was contaminated with a virus.


Of course, it would be crazy to suggest cutting down on fruits and veggies in the hopes of reducing our risk for norovirus or hepatitis. We need the nutrients they provide! But we definitely don’t need the germs they can carry. So follow these tips to stay safe.

Before handling raw fruits and vegetables…

  • Wash your hands in warm, soapy water for at least 20 seconds.
  • Clean knives and other kitchenware (cutting board, colander, scrub brush) prior to each use by running them through the dishwasher or washing well with soap and water.

How to wash produce…

  • Remove and discard outer green leaves from lettuce, cabbage and cauliflower before washing.
  • Wash produce just prior to using (washing it before storing promotes spoilage).
  • Thoroughly wash all produce, including produce that has been organically grown, purchased from a farmers’ market or even picked from your own garden. Also wash fruits and vegetables with tough rinds or skins that you won’t end up eating—you don’t want pathogens to transfer from the food’s surface to the knife and then into the flesh upon slicing.
  • Don’t plop fruits and veggies in the sink while you wash them—sinks harbor lots of germs. Instead, hold produce in your hands or place it in a colander.
  • Wash produce under running water—it doesn’t matter if it is hot or cold. How long you should wash depends (for instance, on the size of what you’re washing), but the point is to be thorough. Rub briskly with your hands to help remove dirt and surface microorganisms…for produce that has a firm skin or a rind, such as squash or melon, scrub with a clean brush under running water.

After washing produce…

  • Trim hulls and stems from items such as strawberries, tomatoes and peppers after washing.
  • Dry your freshly washed produce with a fresh, clean towel or paper towels—not with a dishtowel that has already been used to dry off anything else—and then place it on a clean cutting board or plate.
  • Rewash utensils frequently during produce preparation to minimize the spread of any “straggler” viruses and bacteria that might still be present.

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