COVID Transmissions for 3-4-2022
Long COVID, with longer follow-up, in focus. Other viruses: avian influenza.
Greetings from an undisclosed location in my apartment. Welcome to COVID Transmissions.
It has been 809 days since the first documented human case of COVID-19. In 809, Caliph Harun al-Rashid died. Harun al-Rashid is extremely famous, and was made into a figure of legend in The Thousand and One Arabian Nights. One thing that isn’t legend that he did, however, was give the gift of an elephant to Emperor Charlemagne. That’s right—a ruler living in Baghdad in the year 809 was in contact with a ruler living in Aachen in Europe, and gave him the gift of an elephant.
The elephant, by the way, has its own wikipedia page, something that makes me self-conscious about what I’ve done with my life: https://en.wikipedia.org/wiki/Abul-Abbas
Today, in the “Other Viruses” section, we’re going to talk about the relationship between humans and animals and what this has to do with influenza virus pandemics.
In the free COVID-19 area, we’ll be talking about Long COVID and nerve damage—and contextualizing some broader themes in Long COVID research to understand what may be coming in the future.
Bolded terms are linked to the running newsletter glossary.
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Now, let’s talk COVID.
Peripheral neuropathy in Long COVID
Some readers have noticed that I only write about Long COVID on here periodically. This is not out of personal preference. Rather, it is out of concern that Long COVID is a very complex topic where there remains quite a lot of uncertainty.
While I am certain that there are long-term symptoms that manifest in a large number of people, particularly unvaccinated people, after a bout of COVID-19, what I have tended to be uncertain about is whether “Long COVID” represents a single syndrome, or a set of various conditions that are all long-term impacts of the disease—a distinction which is important if we are to understand how to treat people with long-term effects.
I have begun to favor the latter, and this small study is a great example of why: https://nn.neurology.org/content/9/3/e1146
This is a study of 17 patients with particularly long-term symptoms following COVID-19. Patients in this work were followed for an average of 1.4 years, which is quite a long time when you consider the not yet 2 year length of the entire pandemic.
In this study, 59% of patients had long-term nerve problems that are known as peripheral neuropathy. This is the technical way of saying that they had nerve damage but not in the central nervous system. Peripheral neuropathy can manifest in various ways—pain in the nerves, tingling sensations, loss of sensation, and other ways. It is a symptom that can emerge following some kind of damaging event, or for reasons that are not immediately apparent. It can be temporary, or it can be permanent.
However, it does not simply happen in 59% of the population. One way to explain that finding is to presume that this was luck of the draw, and had nothing to do with COVID-19 at all—the sample just includes a larger than normal group of people, at random, than would get peripheral neuropathy in the wider population. I don’t think we can handwave the result away so easily, not in the context of a paper like this one ( https://www.nature.com/articles/s41598-021-98565-w ), that estimates rates of peripheral neuropathy in adults over 40 with diabetes to be ~28%, and about 12% in the same age cohort but without diabetes. Those numbers are much lower than 59%, so while I do not think this Long COVID paper is necessarily the definitive answer on the rate of peripheral neuropathy as a long-term COVID symptom, it does indicate to me that there is something happening in Long COVID that encourages some elevated rate of peripheral neuropathy. The effect, the frequency, and the mechanism behind it might all be revealed with further investigation—which I encourage.
We could leave it there, but I chose this paper today for a reason, and it’s not just the finding about peripheral neuropathy. There are two more things that stuck out to me. One, not everyone in the study has this symptom—41% don’t. Two, peripheral neuropathy is just one symptom that is associated with Long COVID, something you can verify just by looking at that first fact. If 41% of the people in a sample of patients with Long COVID don’t have peripheral neuropathy, then to have Long COVID, they must of course have some other symptoms.
If this sounds trivial, I promise it is not. An important part of disease research is actually defining the conditions contained within a disease, and how they progress over time. From just this one study we can generate a few interconnected hypotheses:
Peripheral neuropathy may be one of several post-acute COVID-19 sequelae
It appears not to be a universal outcome in those who remain symptomatic after the acute disease
There may be multiple disease processes that are involved in what we’ve been calling Long COVID
If there are multiple disease processes involved, Long COVID may not be one disease but instead a cluster of different ones that all involve long term symptoms after COVID-19 recovery; what may differentiate these diseases is the underlying disease mechanisms and potentially disparate symptoms
None of what I’m saying here is a new idea; the CDC has been calling Long COVID “PACS” for “post-acute COVID-19 sequelae” for quite some time now, on the possibility that we are looking at a set of possible long-term outcomes rather than perhaps a single disease.
However, these suppositions have been based on early observations. As we begin to develop observations like this newer study, which include more than one year of follow up, we will start to have a more reliable sense of what PACS/Long COVID really is, and whether it is even one thing at all. Based on this small study, I’m starting to feel more confident that it isn’t.
While this may sound scary, it also speaks to possible approaches to treatment. Instead of trying to look for one solution for everyone, the approach in a situation where we are looking at multiple outcomes with multiple causes would be more personalized. Perhaps some of these conditions will turn out to be easier to reverse than we currently think.
I suppose only time will tell, and I intend to continue monitoring Long COVID as the science behind it develops. Even when the pandemic is in the rearview mirror, it seems there will still be news about this longer-term disease.
Part of science is identifying and correcting errors. If you find a mistake, please tell me about it.
Though I can’t correct the emailed version after it has been sent, I do update the online post of the newsletter every time a mistake is brought to my attention.
No corrections since last issue.
What am I doing to cope with the pandemic? This:
Playing: Rimworld
I’ve been playing around with a science fiction “storytelling” game called Rimworld. It’s in the same vein as Firefly, about people in the distant future living on the outskirts of a multiplanetary society, but gameplay-wise, it’s kind of a city-builder game. I find it relaxing, and it can run on its own in the background while I do other things—something I definitely like in a game.
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For those who won’t be continuing beyond that into the rest of the paywalled section below—as well as everyone who will—please know that I deeply appreciate having you as readers, and I’m very glad we’re on this journey together.
Always,
JS
Highly pathogenic avian influenza viruses found in bird flocks in Connecticut and Iowa
The USDA has confirmed the presence of highly-pathogenic avian influenza viruses (HPAIVs) in two non-commercial “backyard” bird flocks in the US states of Iowa and Connecticut: https://www.aphis.usda.gov/aphis/newsroom/stakeholder-info/sa_by_date/sa-2022/hpai-ct-ia
Before we lived in a world where COVID-19 became a pandemic, HPAIVs were on the watchlist as likely to cause serious pandemics in humans. They should still be on that watchlist, by the way. But this is not necessarily a story where we should be worried about a simultaneous influenza pandemic, and that’s what I’d like to dive into today.