How much of a help are masks in fighting the Covid-19 pandemic? Absolutely essential, it seems, to New Yorkers. A woman who failed to sport a mask sparked hysteria in a Staten Island supermarket. Other shoppers started shrieking at the modern leper to “get out” (and other less delicate expressions). The governor, Andrew Cuomo, has ordered people to wear masks in public when they are unable to follow social distancing guidelines.

But do we need masks? Are they essential for stopping transmission of the virus?

Residents of Staten Island may be surprised to learn that the experts disagree on this basic feature of everyday experience of the pandemic.

A New York Times article last week stated flatly: “The debate over whether Americans should wear face masks to control coronavirus transmission has been settled.”

That word “settled” is unsettling. It suggests that there is a scientific consensus that the panic-stricken Staten Islanders are right. There isn’t.

Of course donning a mask is far from being a bad idea. If you are wheezing with Covid-19 or even a common cold, a mask will reduce the number of infected droplets that you spray through the air every time you cough or say “hello”. You won’t lose your friends; you won’t annoy fellow shoppers. But will it stop the droplets completely? Will they be infectious? Should everyone wear a mask? Will everyone wear a mask? Must everyone wear a mask?

An op-ed in the New York Times by three experts on public health and human behaviour from the University of Pennsylvania, including the controversial Ezekiel J. Emanuel, makes a strong case for poking the public to wear masks. “Day by day,” they write, “new scientific evidence is demonstrating the efficacy of masks in the fight against the coronavirus.” That was published on May 27.

The link to “scientific evidence” leads to an article in the leading science journal Nature published on April 3.

This was followed by the publication of an article in the BMJ, another prestigious journal, on April 9 by Trisha Greenhalgh, of Oxford University and colleagues. They reviewed the surprisingly meagre evidence for wearing masks and concluded that it is so “simple, cheap, and potentially effective” that they should be worn at home and in public by people with symptoms.

But against this “settled science”, several doctors associated with Harvard Medical School published an article in the New England Journal of Medicine on April 1 which says No – at least for the public.  They write:

We know that wearing a mask outside health care facilities offers little, if any, protection from infection.

“We know that…” – in other words, their understanding of the "consensus" is completely opposed to the “settled science” described in the New York Times. They explain:

Public health authorities define a significant exposure to Covid-19 as face-to-face contact within 6 feet with a patient with symptomatic Covid-19 that is sustained for at least a few minutes (and some say more than 10 minutes or even 30 minutes). The chance of catching Covid-19 from a passing interaction in a public space is therefore minimal.

And they add – as the Staten Island incident proved -- “In many cases, the desire for widespread masking is a reflexive reaction to anxiety over the pandemic.”

Furthermore, they point out that masking could even be counter-productive on a mass scale “if it diverts attention from implementing more fundamental infection-control measures”.

Perhaps masks are less a health measure than a symbol of social solidarity, they say.

… masks serve symbolic roles. Masks are not only tools, they are also talismans that may help increase health care workers’ perceived sense of safety, well-being, and trust in their hospitals. Although such reactions may not be strictly logical, we are all subject to fear and anxiety, especially during times of crisis. One might argue that fear and anxiety are better countered with data and education than with a marginally beneficial mask, particularly in light of the worldwide mask shortage, but it is difficult to get clinicians to hear this message in the heat of the current crisis.

In other words, wearing a mask is a bit like wearing a burka. Apart from keeping your droplets to yourself or shielding you from the sun, it’s a public affirmation of your allegiance to an important cause.

Should wearing masks in public be mandatory in Staten Island supermarkets and elsewhere? Ezekiel Emanuel and his colleagues hint that they should be, based on what they effectively describe as settled science.

But the science is far from settled.

This is a minor issue and hopefully it will soon be history. But it offers a lesson for the post-pandemic world: whenever you hear a consensus yelping, don't pet it, don't feed it. Grab it, shake it, poke it, look in its floppy, silky, best-in-show ears for ticks. You'll find some.