Thanks, DSeid. Inconclusive at this point, since as you say in the first couple of cites it’s unclear how many became symptomatic later; but that’s not surprising. Eventually this info will become clearer.
I saw a piece on ABC’s network news tonight that is related to this mystery of why some people get sick and others don’t. It was about kids who are getting what they are now calling Pediatric Multi-System Inflammatory Syndrome Associated with COVID-19. The kids don’t show symptoms at the time of infection, but 4-6 weeks later get really ill. It’s being considered rare so far, but it seems to stem from an immune system overreaction to the virus. I can’t find a link to the exact thing I saw, but a New York ABC affiliate has one here.
Chilblains might be a symptom common in the otherwise asymptomatic
Several years back, when I was uber skinny and lacking the funds to buy good winter attire, I suffered from a bad case of chilblains. My fingers and toes turned into Vienna sausages for about three weeks. For a hour or so each day during that period (usually starting around 9:30 am), they would itch and burn like the dickens. Once it was so bad that I cried in the restroom at work, desperately running cold water over my fingers to take away the pain. My toes would get so big that I would have to take my shoes off. Finally, I went to an urgent care place and the doctor prescribed antibiotics and steroid cream, thinking I had some kind of bacterial infection. When those remedies failed, I went on google and landed on a description of chilblains.
I wonder if I will develop chilblains if I get the rona.
DSeid,I have a question, something that’s been bugging me for awhile.
How do we know that most of these asymptomatic cases aren’t false positives? I’m not talking about problems with individual tests, like contamination. But could there be an intrinsic design problem with the test itself in that it’s picking up other, milder coronaviruses - or something else - as COVID-19? These tests are really new to the market and don’t have a track record.
And it seems to me one if the big flags that a test like this might be throwing out huge numbers of false positives is “a whole lot of people that test positive don’t get the disease”.
How do they test the test ? Do they test it against every similar known virus or is the testing not that rigid? Could there be an as yet unnamed, really mild new virus that the tests are picking up as COVID?
I’ve wondered about this for a while and I figure I must be missing something. Can someone enlighten me?
The underlying methodology (RT-PCR) is very well established and robust technology. The RT step is unimportant, that just converts RNA to DNA. PCR uses “primers” that are short pieces of DNA that will only bind to a specific sequence in the sample DNA. And the primers come in pairs, so both primer sequences must be present in the sample. The reaction extends between the two primers to produce a piece of DNA that is the length of the distance between where the two primer sequence are located in the sample. So both primer sequences must be present in the sample, and they must be the same distance apart.
Great care is taken to choose primer sequences that are only present in what you are trying to detect, and they are tested extensively first in silico at the design stage (we know the sequence of the human genome and many pathogens that might be present), and then in vitro with actual samples.
Although nonspecific PCR products are common, primer sequences are long enough that it’s extremely improbable that you’d get a systematic false positive of the correct size just by chance from an unrelated genome. If the virus has mutated and another strain is circulating, a close evolutionary relative certainly could certainly give a false positive signal, as you suggest. But it’s easy to check that this is not what’s happening by sequencing the entire viral genome periodically, or just sequencing the PCR product to check the entire sequence between the two primers. That’s not practical for every sample, but it’s certainly practical for (say) every 10,000th sample.
Here’s why I think the most important question to be answered is why some people who test positive get sick and some people don’t.
Most of you (or surely, many of you) have seen these charts of the waves of infection that are likely to happen over the NEXT TWO YEARS at a minimum. This virus is here to stay for the foreseeable future. We can do our best to keep from getting the virus, but how is that realistically possible? Yeah, people like me can stay sequestered pretty much indefinitely with infrequent trips to the grocery store, but younger people not in my financial circumstances have to go back to earning money, their kids have to go to school, they need routine medical procedures, and on and on.
It seems to me that it’s only a matter of time until all (or virtually all) of us are positive for this virus.
Of those who wind up being positive for the virus, some will get sick and some won’t. Some will get sick right away, some will eventually, and some-- it seems-- will not get sick at all. We don’t know this for sure, but it seems to be the case.
Why? What is the difference between those two groups? Is that difference something that will tell us how to keep people who contract the virus (which sooner or later, will be everyone) from getting sick?
That may not be the single most important question from a societal point of view, but it is from each individual’s point of view.
I am going to get this. Ultimately, over the next two to three years, there is no way for me to avoid it. How can I keep from getting sick once I am positive for the virus?
(If and when a successful vaccine appears on the scene-- fine! THAT will be a game changer and maybe a game ender. Not something to count on any time soon. That will not save us in the short run.)
Yes, PCR does such a great job at amplifying tiny fragments of DNA, that even virus pieces may show up as a positive test for SARS-Cov-2, even if no whole virus particles are present. This is hypothesized as one of the reason some people test positive weeks after seeming to recover. It also means that contamination at the testing site, in the lab, or even during the test kit manufacture can all lead to false positives.
This is absolutely being actively investigated. 23andMe and Ancestry (possibly others) are all surveying their users for Covid-19 information. UK Biobank and other academic samples are doing similar things. One of the goals is to look for genetic differences in the patients which are correlated with disease outcome. Genetic differences can quickly (well, in pharmaceutical time scales) become drug development targets. If scientists learn that a particular form of an enzyme or protein is protective, then perhaps a synthetic version of that enzyme is a drug candidate. Perhaps another substance which has a similar affect on the virus’ life cycle needs to be investigated.
NHK World is currently showing a documentary on the outbreak on the Diamond Princess. I saw part of it earlier today and it is currently replaying. If it isn’t available for viewing online yet, it should be after this weekend.
https://www3.nhk.or.jp/nhkworld/en/tv/documentary/20200509/4001358/
If I remember correctly, they mentioned that during testing of passengers they discovered that for those who were asymptomatic the infection was in the lower lobes of their lungs. The passengers who were showing symptoms all had the infection primarily in their upper lobes.