Long COVID
Very interesting news! My hand-wavy metaphor of what this paper from USA (2024-02-02) found is that the body gets allergic to COVID shrapnel. They found that pieces of dead SARS-CoV-2 viruses can recombine with double-strand DNA (dsDNA) to form things that look like antimicrobial peptides — proteins in the native immune system which cause inflammation.
One would think that the body would eventually garbage collect these faux antimicrobial peptides at some point, so at some point the inflammation would stop. I don’t know if the body just doesn’t garbage collect proteins which look like “self”, or if this implies that you can’t have Long COVID for very long without a reservoir of SARS-CoV-2 hiding somewhere in the body.
Testing
This article reports that, despite some social media postings about rapid tests, you should not test your poop. Your feces might have dead virus in them, and there is a delay from how long it takes your poop to move through your system.
Diet
This paper from USA (2024-01-30) found that a keto diet significantly boosted the adaptive immune system, while a vegan diet boosted the innate immune system!
Transmission
This paper from China (2024-01-27) did a very careful study of transmission during Omicron in one classroom, looking at ventilation, density, video of actual student placement/interaction/facial gestures, etc., and made a model of the interactions. They found:
- The risk of infection among students was 1% per 45-minute class. (That might not sound like a lot, but if a student has 15 classes per week and a 16-week semester, they have a 91% chance of catching COVID-19 in that semester.)
- Wearing N95 masks would drop the risk by 96%.
- Increasing the airflow by ~24x would drop the risk by 81%.
- Dropping the occupancy rate in half and placing the students carefully would drop the risk by 62%.
This paper from USA (2024-01-24) found that 75% of people concealed an illness, usually to go to social events or to complete work objectives.
This paper from Sweden (2024-01-27) found that people were pretty bad at estimating how much riskier being close to an infected person was than just a bit farther away. For example, they thought that moving from from 1.5 to 0.5 m away would increase the risk by about 3x, where actually it increased the risk by 9x. (By contrast, people were pretty good at estimating risk reduction from masking)
Pathology
This blog post says that COVID-19 will never be “just a cold” because colds are restricted to infecting cells in the respiratory tract, while COVID-19 — because it uses the ACE-2 receptor which is found in the heart, the brain, the gut, the testicles, the kidneys, blood vessels, the liver, the thyroid, and more.
I am a little confused. If you assume that the author is using “a cold” as a shorthand to mean “a mild upper respiratory disease”, maybe that means flu, and flu can have long-term non-respiratory effects:
- The Spanish Flu (an H1N1 influenza A virus) led to cases of sleeping sickness, and later Parkinson’s. (Probably. Possibly.)
- Getting a flu shot cuts your risk of a major cardiac event (e.g. heart attack, stroke, heart failure) in the next year by 50%.
In addition, some “common cold” coronaviruses enter cells via the sialic acid which is on all cells. I am working on understanding this.
This paper from China (2024-01-31) found that Beta was the variant with the highest case fatality rate (CFR). Worldwide, they calculated the CFRs as: Alpha: 2.62%, Beta: 4.19%, Gamma: 3.60%, Delta: 2.01%, Omicron: 0.70%. (By contrast, Wikipedia says that the CFR for influenza is < 0.1–0.5%.)
Mitigation Measures
This paper from USA (2024-01-26) found that healthcare workers failed a mask fit test 38.7% of the time after using a mask for one full shift. The failure rate was best for dome-type, very slightly worse for duckbills, and a lot worse for trifolds:
- dome, 25.8%;
- duckbill, 28.3%;
- trifold, 61.3%.
Vaccines
This paper from USA (2024-02-01) found that the XBB shots are quite effective against what is circulating now. They found it was 54% effective against symptomatic infection after an median of 52 days. That might sound low, but remember, the controls are going to be people who might have had non-XBB shots and/or infections.
Treatments
This paper from USA (2024-01-30) found, again, that the gut biome was important in respiratory disease resistance. Mice with particular type of bacteria (segmented filamentous bacteria or SFB) resisted respiratory diseases: the SFBs altered basally resident alveolar macrophages (AMs) in the mice to be much better at calling in the innate immune system cavalry to kill off the respiratory infections. When they transplanted the SFB-altered AMs into mice without SFBs, the AMs still did a good job of killing off respiratory infection viruses.
This sounds a little like vaccination to me. Maybe the AMs “learn to kill” the SFBs, and that just happens to help killing the respiratory diseases?
Recommended Reading
This post argues convincingly that most of the lifespan extensions of the first half of the 20th century were not from “medical advances” as much as “public health advances”.