Researchers probe COVID-19’S weirdest symptom

Anosmia: the loss of the sense of smell. The anecdotal evidence that anosmia is a symptom of SARS- COV- 2 seems overwhelming, and there are many colourful case reports popping up in the ear- nose- and- throat ( ENT) literature, but very little has been done to put this surmise on a scientific footing. Perhaps the nearest thing that exists at the moment is a shred of correspondence from Iran, which got hit by the virus early and hard.

It’s a sketchy paper that popped up March 27 on medrxiv, a website for immediate publication of “preprint” research that has not yet been scrutinized and vivisected by peer reviewers. ( Medrxiv was founded in June of last year — it’s a conscious imitation of analogous sites that serve math, physics and biology — and in the current crisis it is being considered an enormous blessing, though probably not an unmixed one.)

The Iranian study isn’t very rigorous (it is “ecological,” a term applied with mild scorn in medical research), but it’s probably telling all the same. As COVID-19 descended on the country in March, doctors were receiving so many reports of anosmia that the country’s Medical Council created a questionnaire especially for sufferers and spread the word about it on social media. After cross- checking people’s answers and throwing out the dodgy ones, they ended up with over 10,000 electronic reports of smell- blindness, in numbers well correlated with the local prevalence of detected COVID- 19 cases. Three- quarters of the respondents had had recent “flu,” but few were still experiencing flu symptoms when they answered the questionnaire.

Only the sheer volume of the reports — and maybe the fact that anecdotal evidence was strong enough to get the country to put together a questionnaire in the first place — has any power to convince. The authors of the Iranian study more or less throw up their hands and say “Well, we have what looks like a huge ‘outbreak’ of anosmia, and you all know what’s happening with COVID-19 here. None of the other stuff that would normally cause anosmia, like head injury, is happening here in epidemic quantities. There’s not much else we can tell you. Connect the dots.”

In Britain, the anecdotal association of anosmia and COVID-19 has ENT specialists wondering whether loss of smell should be formally considered a diagnostic sign. I suspect that at this point every physician on planet Earth actually would, for treatment purposes, consider it a diagnostic sign. The issue is with official public health doctrine. Should people who experience sudden anosmia be urged, or forced, to self- isolate? The public- health hive- mind won’t act on this until there is good evidence, or the credible appearance thereof. By the time they decide to, we shall hopefully be testing so many persons directly for viral RNA of SARS- COV-2 that symptomology will be somewhat irrelevant.

Meanwhile, ENT doctors are trying to guess at possible “mechanistic” explanations for why SARS- COV-2 is doing this creepy, science- fiction- y thing. Other coronaviruses have been shown to cause temporary anosmia: disturbingly, the original- gangsta SARS was found in mice to have accomplished this by reaching the nervous system through the nose and killing neurons.

The most r espe c t - able- looking early study of SARS- COV- 2 and scent ( this one a biorxiv preprint from an Avengers- like squad of international docs and statisticians) suggests that SARS The Sequel is probably not attacking the brain — just the “olfactory epithelium,” the surface tissues in the nose and throat that transmit scents to the brain’s “olfactory bulb.” This sounds like good news, but the study authors warn that post- viral anosmia could be quite persistent in some cases.

( One issue is that the enzyme ACE2 is strongly suspected to be SARS- COV- 2’s pathway to the body, but the significance and genetic nature of ACE2 were only themselves discovered practically yesterday.

So anyone researching anosmia and SARS- COV- 2 has to start out by establishing very basic facts, not already known, about the relationship between ACE2 and olfaction.)

Could we end up with a generation of COVID anosmics, living the balance of their lives with only four wits about them as those born after 2020 marvel at their oddity? Probably not, but it would make for a good short story. The congenitally anosmic already lurk among us, in very small numbers. There is some compelling non- fiction about them: I recommend A World Without the Olfactory Dimension, written by an anosmic Catalan philosopher, Marta Tafalla. She was nine or 10 years old when she finally figured out what nobody around her had suspected, and announced, out loud: “I can’t smell.”

A kindly doctor told her “It’s not important,” answering her three- word announcement with one of his own, and this was reassuring to a child. But as an adult she can’t help wondering what she is missing, and she must compensate carefully for her missing sense. Anyone who is severely colour- blind, like myself, will know just a little of how she feels.

WELL, WE HAVE WHAT LOOKS LIKE A HUGE ‘OUTBREAK’ OF ANOSMIA.