One particle of Covid-19 typically measures 100 nanometers in diameter.

That is a ten-thousandth of a millimetre; invisible, in other words.

This is a new human drama on an enormous scale, and in our highly visual culture, it calls for an image more vivid and more emotionally resonant more than any line graph.

Masks are, suddenly, all around us.

As French designer Anne Sophie Cochevelou's work with masks shows (Article lead image above), masks can become extravagant face coverings, adorned with anything she can find, from Barbies to Pokemon toys.

So as the world begins looking ahead to a post-lockdown world, face masks look set to play an increasingly central role in our lives.

The latest Lyst Index, a quarterly report that analyses the behaviour of 9 million shoppers each month to track consumer demand, reports a 496% surge in searches for face masks in the last quarter.

The report names the Off-White arrow logo face mask – retail price $95 (£75), now inevitably sold out – as the most coveted buy of the moment.

Some analysts are suggesting that the face mask could overtake the trainer as the best-selling accessory for mass market fashion.

”Best-selling accessory” is, of course, deeply unsettling phrasing when discussing protection against a deadly disease.

But the demand for face masks is about more than their efficacy, about which consensus remains elusive.

Disposable gloves, which can play an important role in hygiene but are not in our eyeline in the way that masks are, have a low profile by comparison.

Mask-wearing is not just about doing the right thing, but about being seen to do it.

Mask-wearing is becoming more common as people find that the embarrassment of being the only person in the supermarket without a mask outweighs the self-consciousness of wearing one.

In the pavement-dance of physical distancing, a mask is a way of signalling to others that you are a responsible citizen – not the runner to barge sweatily past others, nor the shopper who squeezes all the melons while breathing heavily.

Fashion has always been about both fitting in and standing out.

Mask wearing can be a way of pledging allegiance to good citizenship – like wearing a poppy in the first week of November, or a T-shirt in support of health workers – and an opportunity for self-expression.

There are sleek high-tech masks and there are sweetly homespun ones; there are designer logo masks and sloganned high-street ones.

Jeans, running shoes, even sunglasses: many of fashion’s hero products have utilitarian roots. Although where mandated by law as it already is in some regions, the mask will bring new meaning to the phrase “must-have”.

The New York-based fashion brand Collina Strada is selling brightly coloured masks fastened with ribbon-trailing bows, made from deadstock fabric from past collections.

The masks, which have an opening to insert a filter, retail for $100; for every one sold, the brand donate five to healthcare workers.

A note on the website adds: “If you or a loved one is sick and this is out of your price range, please reach out to us directly we have other masks available to send to you at no charge.”

Fashion can be tone deaf at moments such as this.

Boohoo was quick to market with jaunty £5 fabric masks, with the slogans “Eat, sleep, isolate, repeat” or “If you can read this, you’re too close”, but withdrew them swiftly after a backlash.

But many designers want to put their skillset to good use, rather than plunder panic for profits.

The independent London fashion week designer Christopher Kane offered on Instagram to post unused fabric and a simple mask-making pattern to anyone who asked.

Having now fulfilled thousands of requests, the studio has used up all its fabric, but has made the pattern available to download, so that you can make a mask at home with any cotton fabric, and ribbon.