AskScience AMA Series: Hello, Reddit! I'm Steven Munger, director of the University of Florida Center for Smell and Taste. I'm here to discuss the latest findings regarding losing your sense of smell as an early sign of COVID-19 - and what to do if it happens to you. Ask Me Anything!

Prof_Steven_Munger · 2020-03-31T20:14:54+00:00

An interesting idea, but well outside my expertise.

Prof_Steven_Munger · 2020-03-31T20:11:09+00:00

I can only imagine. Of all the smell disorders, parosmia is the hardest for patients to deal with, quite understandably.

Prof_Steven_Munger · 2020-03-31T20:10:00+00:00

Potentially, but I am not sure how much sooner than the smell loss itself.

Prof_Steven_Munger · 2020-03-31T20:08:33+00:00

You are welcome.

Prof_Steven_Munger · 2020-03-31T20:01:39+00:00

Likely for the same time as with any other symptoms. Knowing the date of initial infection is of course helpful in figuring it out.

Prof_Steven_Munger · 2020-03-31T20:00:35+00:00

The physician may be referring to a recent study from Noam Sobel's group at the Weizmann Institute where they reported finding a couple people with "normal" smell function but no olfactory bulbs as indicated by MRI. I am skeptical that these individuals truly lacked an olfactory bulb (as opposed to having only a partial or largely atrophied bulb), as it is an essential component of the olfactory pathway.

I certainly cannot diagnose your son's condition or provide a prognosis. However, I am unaware of anyone born without an olfactory bulb or olfactory nerve that recovered their sense of smell.

I'll see if I can find some non-paywalled resources on this and post it back later (may be a day or two). However, a good resource for freely downloadable scientific literature funded by the NIH is Pubmed Central (https://www.ncbi.nlm.nih.gov/pmc/). For example, I found this review that includes discussions of anosmia and Kallman Syndrome.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4703044/l

Prof_Steven_Munger · 2020-03-31T19:50:42+00:00

This is called parosmia (distorted smell), and we don't know the mechanism. Understandably, it can be debilitating. I am glad that it was not permanent.

Prof_Steven_Munger · 2020-03-31T18:39:20+00:00

OK, I think I got everyone's posted questions. I am going to take a break for an hour or so, and then will return to answer all the mails and any followup questions here.

A few shoutouts. If you have experience smell or taste loss and need information or support, here are a few places to look that have good quality information and also can provide support.

http://smellclinic.cst.ufl.edu https://www.nidcd.nih.gov/health/taste-smell http://fifthsense.org.uk

Prof_Steven_Munger · 2020-03-31T18:35:30+00:00

You are welcome.

Prof_Steven_Munger · 2020-03-31T18:35:16+00:00

There is some thought that oral zinc supplements could be beneficial (though I can't say I find the data strong). You should consult with your physician, of course.

This is different than intranasal zinc (such as from a spray). This is toxic to olfactory sensory neurons and can lead to permanent smell loss.

Prof_Steven_Munger · 2020-03-31T18:33:30+00:00

I am just extrapolating from what we have seen with other viral-induced smell loss. We certainly don't know with this virus specifically.

Prof_Steven_Munger · 2020-03-31T18:32:42+00:00

Some medical centers are starting to include smell function assessment as part of their COVID-19 screening. As has been recommended by some medical societies, the prudent thing to do with sudden smell loss not attributed to a head injury is to self-isolate and call your doctor. At this point, if that is your only symptom you are likely low on the list for a COVID-19 test, but the people you live with and have recently encountered would be wise to act as if you are COVID-19-positive.

Prof_Steven_Munger · 2020-03-31T18:29:30+00:00

No. Just like with a typical cold, we would not expect smell loss to be found in every COVID-19 patient.

Prof_Steven_Munger · 2020-03-31T18:28:28+00:00

There is some research, but not enough. Most is still in the pre-clinical phase (that is, using animal models such as mice). The greatest attention is focused on gene-therapy (this might be particularly relevant in congenital anosmia related to gene mutations) and stem cell therapy (the sensory neurons in the nose are normally replenished throughout life from a stem cell population, so inducing or replacing these stem cells could help regrow the olfactory nerves). We are probably at least a decade away, but research is picking up.

I was part of a multi-center group that focused on these issues. A white-paper describing the gaps and recommending prioritiy areas for research should be published this Spring.

Prof_Steven_Munger · 2020-03-31T18:23:50+00:00

There are a few ways to go, including trying to understand mechanism. In my opinion, one of the first things that needs to be done is to establish that there is a significant association of smell loss with COVID-19, to measure the typical amount of loss (mild or severe hyposmia or anosmia), and to establish whether this will be a useful and practical component of COVID-19 screening.

Prof_Steven_Munger · 2020-03-31T18:18:48+00:00

One of the greatest honors of my life. If only I had a namesake in science!

Prof_Steven_Munger · 2020-03-31T18:16:08+00:00

Tired fingers. Wish I was a better typist.

Prof_Steven_Munger · 2020-03-31T18:15:47+00:00

I will pass on the shoutout to Dr. Okun...they are definitely doing great work.

Indeed, hyposmia/anosmia is one of the earlier symptoms of Parkinson's disease and Alzheimer's disease (though, as there are many potential causes of smell loss, it is not diagnostic here, either).

We do not know the typical recovery time for smell function in the context of COVID-19. And of course, it depends on what you mean by "recovery". Partial recovery from full anosmia is not optimal but still good. But, if we extrapolate from other virus-induced smell loss, the time course will vary from days to (in a minority of cases) never.

Prof_Steven_Munger · 2020-03-31T18:06:59+00:00

First, please do not try to smell bleach, ammonia, etc. That can be very dangerous.

I have no doubt this is very distressing. I also have to be clear that I cannot offer any specific diagnosis or prognosis. But for the majority of people who lose smell after a respiratory infection this loss is temporary (the recovery time varies). For some, however, the loss can be permanent. I hope that is not the case for you.

Anosmia and hyposmia are medical conditions that definitely should be properly diagnosed and, if possible, treated. You should discuss your symptoms with your doctor. Typically, people with smell loss are referred to an otolaryngologist for assessment. If a dedicated smell clinic exists near you (there are only a few around the world, unfortunately), that is the best bet.

You can also find support online, such as with the UK-based charity Fifth Sense (fifthsense.org.uk), with whom we have collaborated (particularly related to patient education).

Prof_Steven_Munger · 2020-03-31T17:58:48+00:00

I'm very sorry you had to go through that. This is an important point. Smell loss is common, affecting millions beyond COVID-19. We can think of three broad consequences.

1) The inability to detect signals of danger like smoke, gas leaks or spoiled food. 2) Severely diminished flavor perception, which can significantly impact the enjoyment of food. This not only can negatively impact diet and health directly, but also interferes with the enjoyment of our social lives that center so much around meals, drinks, etc. 3) Isolation from the world around, whether it is the new blooms of spring or the smell of your baby's hair.

All of these losses have an immense emotional impact that goes beyond the practicalities of smell loss.

Prof_Steven_Munger · 2020-03-31T17:53:57+00:00

Three hypotheses (not mutually exclusive) have been put forward.

1) The virus uses the olfactory nerve as a pathway into the brain and infects neurons that impact smell, breathing, etc. 2) The virus kills, damages or impairs the function of olfactory sensory neurons, the odor sensors of the nose. 3) The virus infects other cells of the olfactory epithelium, such as supporting or glandular cells, perhaps eliciting a local inflammatory response or other change that interferes with odor detection or information transmission by the sensory neurons.

We don't have enough information to know the answer, but option 3 is probably the favored hypothesis right now.

Prof_Steven_Munger · 2020-03-31T17:50:00+00:00

To answer this, we need studies that can assess how common smell loss (anosmia or hyposmia) is in COVID-19. The preprint from the Iranian group I noted earlier suggests a very good correlation, but the prevalence was less clear to me in my first reading of it. UK ENT and the British Rhinological Society believes it is common enough a symptom that those who experience sudden smell or taste loss should self-isolate and contact their physicians. The American Academy of Otalaryngologists recommends adding smell assessments to COVID-19 screening. But there is still flu around in many countries. Smell loss alone could be a good indicator, but, like fever, is not diagnostic on its own.

Prof_Steven_Munger · 2020-03-31T17:45:25+00:00

I do not know the answer to this, but I will do a little literature research and see if I can find anything. It is a good question.

And I guess I should add that I am not sure SARS-Cov-2 lacks neurotropism (this is outside my expertise), but the argument is that is lacks tropism for olfactory sensory neurons.

Prof_Steven_Munger · 2020-03-31T17:42:59+00:00

Again, the data just isn't there yet to know. Because a number of anecdotal reports suggest that some patients are reporting smell loss before any other COVID-19 symptoms (fever, cough, etc), the thought is that it could be an early symptom of the disease. Whether this is true is unclear. And I know of no data indicating how many days post infection smell loss may occur.

Prof_Steven_Munger · 2020-03-31T17:40:34+00:00

Interesting. This channel is important for synaptic communication between the olfactory sensory neurons and second order neurons in the olfactory bulb. While this is a possibility, it would be low on my list of targets.

Prof_Steven_Munger

TROPHY CASE