Scarves, friends, the example of the US president, can any of them help you follow the latest health advice?

“I haven’t touched my face in weeks,” said Donald Trump, at a meeting with airline CEOs about the coronavirus crisis on Wednesday. “I miss it.”

Twitter users promptly found recent photos of the president with his hands all over his chops, claiming to have caught him in a lie. But in this case, Trump may have revealed a fundamental truth of life in the time of Covid-19: it is really, really hard to resist touching your face.

𝓒𝓪𝓷𝓭𝔂 𝓗𝓮𝓪𝓻𝓽 🍬❤️ (@nkosibooi) #CoronaVirusChallenge

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On Friday morning #CoronavirusChallenge was trending on Twitter, sparked by footage showing a health official from Santa Clara county, California, licking her finger during a briefing. She had just advised the public: “Start working on not touching your face, because one main way viruses spread is when you touch your own mouth, nose or eyes.”

It is a simple strategy of prevention: the virus can live for at least nine hours, and possibly days, on hard surfaces. But it is easier said than done.

As many of us have become uncomfortably aware, not touching your face is like The Game, wherein as soon as you think of it, you lose.

Told not to touch your face, I guarantee: you will be able to do little else – even with the risk of becoming a coronavirus casualty.

I tried for a day on Thursday, sightseeing on holiday with a friend. “I’m trying not to touch my face,” I told her. “If you see me doing so, please stop me.”

This did not work, for reasons that are obvious in hindsight: if your friends notice where you are putting your hands, your hands are either somewhere entirely inappropriate, or your friends’ attention is too close.

I myself became excruciatingly conscious of where my grubby mitts were going – but only with something like a two-second delay.

I applied too much lip balm. My fringe settled unflatteringly. I felt an overpowering and, I am quite certain, psychosomatic urge to itch my ear, my eyebrow, my nose. Every time, I instinctively touched my face – and every time, I checked myself too late.

My friend watched in bemusement. While I spasmed whenever my hand drifted north of my collarbone like a woman possessed, she had landed on an elegant solution: keeping her hands as clean as possible, draping them in a scarf before she touched the grab bar on the tram or exchanged money.

Simply adjusting my own scarf seemed impossible to do without coming into contact with my face – if indeed my scarf, going between covering the backs of restaurant chairs to the lower third of my face, was not a potential Covid-19 carrier.

Play Video 4:31 How to stop the spread of coronavirus – video explainer

My new awareness of my extremities served as a reminder: even for those of us fortunate enough to have not been directly affected by coronavirus, every gesture has become loaded.

Out in public – on the train, or on a bank note – you might imagine you can see the infectious fingerprints. It is a distressing way to view the world, but it may be the necessary prompt to take the threat seriously.

With willpower alone proving inadequate, I have now resorted to machine learning to help me practice vigilant hygiene. The website donottouchyourface.com uses your computer’s webcam to train an algorithm to recognise when you are touching your face.

When you do so, the screen flashes red and a disembodied voice sternly tells you “NO”, like you are a disobedient dog. When the tool is open in a background tab, a pop-up notifies you: “You touched your face.”

The idea is that, over time, “you learn to stop touching your face”, say the tool’s developers. Their answer to the frequently asked question: “Will this stop me from getting Covid-19?” is a tentative: “Not for sure, but it might help.”