Loss of taste or smell is one of the strongest signals for COVID-19. Though not every COVID-19 case has this symptom, it's a very specific symptom that doesn't commonly have other causes. This question is about the suitability of coffee beans as a low cost testing tool for COVID-19. I'm interested in exploring this as I lead development of the WHO COVID-19 app.

The Odds Ratio for a person reporting loss of taste or smell was reported as 6.7 through the COVID Symptom Study in their Nature research paper: Real-time tracking of self-reported symptoms to predict potential COVID-19. Overall AUC reported as 0.75 for all user symptoms. It's not accurate enough to be a diagnosis but it can be combined with other symptoms, cough recording and COVID exposure information to improve accuracy to do screening for further tests. The question is whether adding a specific daily smell test using coffee beans would be worthwhile?

The general thought is to have a cup of coffee beans that you smell on a daily basis. Then report in the app if you had a loss of smell. The ideal test is fast, cheap and easy. To be fast, the container may need to be open so you don't have the daily irritation of having to remove a sealed lid. I considered a coffee bean as I thought they'd be cheap and available around the world.

If you'll excuse multiple questions, I have some specific areas I was looking for feedback on....

  1. How to get consistency in smell? Smell decay curve for coffee beans. How quickly does open coffee beans lose their smell? How does an open / closed container impact this? How often might you need to replace the beans due to smell decay, mold or other reasons?

  2. Cost of coffee beans. How widely available and affordable are they in some of the poorest communities in the world?

  3. Any other product that you think that could be more effective. It needs to be an existing widely available low cost product.

Please share any other thoughts or feedback you might have.

  • I'm not sure if you're still looking at this, but from people who've had this symptom I heard they couldn't smell dirty diapers or (cleaning) alcohol anymore. I guess these two smells might be more accessible. Especially cleaning alcohol could be a good test now that it's available in many public places and people are encouraged to wash their hands with it.
    – JJJ
    May 6, 2021 at 10:41
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    U Smell It is a startup that has focused on this technology: usmellit.com May 10, 2021 at 23:13

1 Answer 1


Fresh coffee is neither widely available nor inexpensive in all places. Coffee in Japan is relatively expensive because demand is relatively (extremely) low compared to western nations. I think I remember my coworkers also telling me that fresh coffee in India is almost never used because most Indians so drink coffee prefer instant. I wouldn't trust availability of coffee for this kind of test, but it also can't hurt to include it in the app as an option for people who can get fresh coffee.

I say fresh coffee because instant coffee in my experience doesn't have a strong smell in the first place.

About smell decay, that depends on a wide range of factors such as time since roasting at time of sale, quality of beans, conditions of storage, and qualities of packaging. My experience with cheap coffees is that they tend to be sold preground (which will lose scents faster than whole bean), though this will not be true in all countries or even all regions within a country.

Does it even matter though? My interpretation of the "loss of smell" symptom of COVID, having not experienced it myself, is literally a complete loss of smell. It would be far more reliable to advise acquiring a new bag of coffee and seeing if you can smell it.

Then again, there are loads of more economical options. Basically every spice under the sun (onion powder, garlic powder, curry powder, chili powder, cumin, paprika, oregano, thyme, rosemary, etc.), aromatic vegetables like onions and garlic, vinegar, fish or fish oil, and other aromatic foods might be more widely available at lower prices than coffee in most places.

  • Thanks. There’s some good points in here. The challenge of asking someone to “acquire a new bag of coffee” is that you want them to take the tests every day. Catching the Symptom earlier and more reliably is the value. Certainly other spices could work. What matters is the consistency and duration of the smell. My guess was that the whole beans would last longer than ground coffee for example. Jan 24, 2021 at 21:30

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