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There are 2 contradicting messages out there that mandate this question:

  1. "It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes." Refer CDC page1.

  2. "Currently, there is no evidence to support transmission of COVID-19 associated with food. Based on information about this novel coronavirus thus far, it seems unlikely that COVID-19 can be transmitted through food – additional investigation is needed." Refer CDC page2.

So, my question now: As per #1, it could spread when we touch an infected surface and touch our mouth. But as per #2, there is no evidence that touching infected food and eating it (food touching our mouth) will cause it.

Why is it that in #1 they seem to be more sure that it will transmit and in #2 they seem to look for evidence ?

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I would tend to think of coronavirus stability from a biophysics point of view. The virus is a small droplet of water inside a lipid membrane, with some proteins in the membrane and a bunch of proteins+RNA packed inside. It is very sensitive to Kampf 2020 (a) detergents - these dissolve the membrane and presumably cause the contents to spill out, (b) RNA damaging agents (such as UVC) - there is no nucleic acid repair machinery so even a single RNA break is likely to inactivate the virus, and (c) denaturing agents (such as heat) - if enough of the proteins are denatured it would stop being able to get into cells. Alcohol is both a detergent and a denaturing agent (over 60% conc). Note that dehydration does not affect the virus much either way: it is stable in water, but also stable if completely air-dried out: "able to retain viability for 3-5 days in dried form or 7 days in solution at room temperature" Chan 2020 (probably because enough water is retained to allow it to rehydrate without damaging the structure). It would decay with time, very slowly (days to weeks) and it may also be eaten by bacteria or fungi (that eat anything organic) which may be a much faster process. A meta-analysis of 26 studies that measure inactivation under different conditions is in Guillier 2020.

From that perspective, coronavirus in food would be expected to be quite stable at least over a few days to a week. It would only be inactivated by heat, or possibly lipid or protein digesting enzymes. How much heat is not clear, but there is no reason to think the coronavirus proteins are either especially thermally stable or unstable - so as a ballpark enough heat to cook meat, or boil an egg (both involve protein denaturation) would also be enough to denature most coronavirus proteins. A fridge, or especially freezer, would extend the half life considerably (weeks to months; "SARS-CoV-2 in solution ... remained viable for up to 14 days at 4°C" Chan 2020). There is very little specific evidence on the stability of any type of coronavirus in food (as opposed to on the surface of packaging, or in water), but what little exists points to persistence for several days, again with much longer times at lower temperatures (eg for MERS-CoV in milk, 37% viable after 72 h at 4°C; this and other studies are reviewed in Olaimat 2020).

Note that cooked food which is contaminated after cooking would be just as problematic as raw food. It would have to be re-heated just before eating to be safe.

Okay, assuming coronavirus is stable in food: is it possible to get infected by ingestion? Probably yes, or at least it cannot be ruled out: "SARS-CoV-2 spread from staff to food products or food surfaces is conceivable" Ceylan 2020 and "SARS‐CoV‐2 may also have the potential for foodborne and waterborne transmission" Aboubakr 2020. SARS-CoV-2 often manifests with GI symptoms first, and may infect the GI tract: "there is mounting evidence that SARS-CoV-2 infection also involves the GI tract" Ding 2020; it is excreted in feces Yeo 2020 and is present in saliva Azzi 2020; and the oral route is the primary route for transmission of non-human coronaviruses such as MHV, BCoV, feline enteric coronavirus and others (also from Ding 2020). Even if the oral route is not very effective, it would be quite surprising if SARS-CoV-2 was completely non-infectious orally.

P.S. Regarding the CDC pages you quote, pay close attention to the wording: "there is no evidence that X" doesn't mean that there is any evidence that X is not true either; it may mean simply that nobody has tried to do an experiment like that and so there is no (direct) evidence either way. Even so, it may be reasonable to think that X is likely to be true because of logic and indirect information (as here).

P.P.S. Note that most things that inactivate the virus would cause an exponential decay in the amount of viable virus. So "stable for a week" doesn't mean there is 100% active virus at 6 days, and 0% and 8 days; it means that half of it would be inactivated in a week, half of the remainder in two weeks and so forth.

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  • Perhaps you could enhance this part "is it possible to get infected by ingestion? Yes, probably (from theory/circumstantial evidence)" – I likeThatMeow Jun 13 at 19:24
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    @CareyGregory Added - let me know if there is anything else specific which you think needs a reference. – Alex I Aug 30 at 0:28
  • Nice! Thanks and +1. – Carey Gregory Aug 30 at 2:19
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I think what they are intended to convey is that they feel that the cooking process will destroy any virus found in food so cooked food should not be a source of infection. Of course that is subject to more data.

However, it is clearly a different proposition if the person preparing the food is infected and contaminates the food after it is cooked. In which case it just it becomes another surface that can transmit the virus.

Although it is currently a matter before the police the thought is that an infected member of crew on board the Ruby Princess was handling food and that's how they managed to infect so many passengers.

https://www.rnz.co.nz/news/world/414144/covid-19-waiter-or-food-handler-obvious-point-of-transmission-on-ruby-princess

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    Just an anecdotal comment, but I eat lunch out quite often, and although I used to eat salads and cold sandwiches and such quite frequently, I've sworn off all uncooked foods from outside my house for now. I can't be sure the guy chopping lettuce in the kitchen is following proper food safety procedures, so cooked food only it is. – Carey Gregory Apr 21 at 0:31
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    No salads for me either! – Graham Chiu Apr 21 at 0:33
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The short answer is that no one is entirely sure right now (more studies, yadda yadda yadda). But, the consensus seems to be that, with proper precautions, yes, it is safe.

The short of it is that yes, food is a surface like any other. However, hot food likely inactivates the virus, but even cold food should be safe to eat because your mouth and stomach are environments that are inhospitable to most viruses. So, what goes into your mouth will likely not infect you, but you should wash your hands after handling your meal and not touch your face while eating to minimize spread from the food to mucous membranes, open wounds, etc (basically, treating your food as you would any other potentially compromised surface, other than putting it in your mouth - please don't do that with most other surfaces).

While the mouth is a mucous membrane, the exposure from mildly contaminated food should be low enough that your body's normal response will be adequate to prevent infection. Note the "mildly", though. Proper food handling techniques should ensure this, but food prepared under questionable conditions would be bets avoided (and not just because of risk of COVID-19 infection).

References:

https://www.forbes.com/sites/victoriaforster/2020/03/25/is-eating-takeout-food-safe-during-the-coronavirus-pandemic/#55c0ce912bd1

https://www.npr.org/sections/health-shots/2020/04/08/822903487/how-safe-is-it-to-eat-take-out

http://needtoknow.nas.edu/id/infection/encountering-microbes/entering-the-human-host/

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