Can groceries be contaminated?

Q: “What should I do to prevent COVID-19 when I come back from the grocery store?” Should I wash the packaging and the fruits and vegetables? ”Asks Nadine Maltais, from Quebec.
A: The first study on the stability of the virus on dry surfaces, such as packaging, was published on February 24 in the New England Journal of Medicine.

The researchers sprayed an aerosol containing the coronavirus on different surfaces and watched after how long it disappeared. They observed that it is still detectable for up to 24 hours on cardboard and up to three days on a stainless steel or plastic surface.

We can therefore certainly find traces of the virus on the packaging of food that comes from the grocery store. And we can assume, even if it was not in the study, that the virus resists for some time on fruits and vegetables.

To minimize the chances of catching it with your grocery store, you can follow the recipe offered by the chemist Normand Voyer: first, drop all your groceries in one place when you get home, then wash your hands with soap and clean with an ordinary household cleaner the handles that you have touched, then put on dishwashing gloves and put all the purchases in soapy water, let them dry on a cloth and then put them away in the fridge or in the cupboards. Putting food directly in the freezer or fridge does not inactivate the virus. Keep products packed in cardboard in a corner and leave them there for at least 48 hours.

But is it really necessary to do all of this? Taking action, if only by washing your groceries, is a great way to reduce anxiety. And it is certain that this reduces the risk. So if you feel the need to do it, go for it! But be careful not to feed your fears or family baffles with that: everyone’s mental health, at the moment, is extremely important!

Also remember that the risk of getting infected in this way is still slim.

Viruses are not living microorganisms, like bacteria or mold. They cannot multiply on their own, but for this they need to be housed in the cells of a living being. So when they land on an inert surface like cardboard or plastic, their concentration always goes down.

The amount of virus found in the sputum of a sick person is enormous. The one on his hands is already less, because the viruses are no longer in their “culture broth” as in the throat or the lungs. This amount is zero when the person has just washed their hands according to the rules of the art. The amount of virus found on objects that his hands touched when they were dirty is probably lower than on his dirty hands, and it decreases over time.

So certainly, a person carrying the virus could have contaminated the packaging of a product that you bought. But for his virus to make you sick, you would have to:

– whether this person went to or works at the grocery store

– that she threw the virus into her environment while coughing or with her dirty hands

– the virus has landed on the product you purchased

– that it happened in the days preceding your visit to the grocery store

– that you have not washed your hands after having stored or touched your grocery store, while the virus may still be present on its surface

– that you put your “dirty” hands on your face

– the virus has passed from your face to your respiratory tract

– that it has multiplied there.

This is a lot of steps, and therefore a lot of chances that the transmission sequence will stop at one time or another.

The measures taken by public health authorities aim precisely to break this sequence. Require everyone who is sick or who has recently traveled to stay at home rather than going to work or going to the grocery store, demand social distancing, ask everyone to wash their hands often and encourage disinfection of their environment immediate more than usual makes contamination from grocery packaging even less likely. But the more people there are sick, the more the risk increases that we find the virus everywhere.

Frequent hand washing and social distancing are more effective than anything else in protecting us. Each new measure reduces the risk, and we can always do more, but the gains can be increasingly small, for ever greater efforts. It is for this reason that the authorities are progressively advancing their requirements, as they see how the risk evolves, depending on the number of people already carrying the virus and the ease with which it is transmitted. .

For now, they don’t require us to wash our groceries. Perhaps they will change their minds, depending on how the epidemic evolves. Monitor the instructions regularly.

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COVID-19 raises a lot of questions. In order to respond to as many people as possible, science journalists have decided to join forces. The media members of the National Cooperative of Independent Information ( Le Soleil , Le Droit , La Tribune , Le Nouvelliste , Le Quotidien and La Voix de l’Est ), Québec Science and the Déclic Center team up to answer your questions. . You have some? Write to us . This project is made possible thanks to a contribution from the Chief Scientist of Quebec , who invites you to follow him on Facebook ,Twitter and Instagram .

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