Covid-19 Asymptomatic - Not what you may think
Caveat: There is a lot yet to learn about Covid-19 and I am not an expert in infectious disease. That said just a couple of months ago most experts were saying that face masks weren't that important for the general public and there was no ability to spread if you didn't have a fever.
Covid-19 Asymptomatic - Not what you may think
One thing that I have been curious about is why the Spanish flu of 1918 was so deadly to young and younger adults and in comparison the same group seems to be spared with Covid-19.
First, being asymptomatic to a virus does not mean that you fought the virus off and your body did so a great job that you had no symptoms - on the contrary - it means that your immune system does not recognize the virus and didn't fight it in the first place. Experts believe this is very rare in regards to viruses and especially to the percentage of people with Covid-19 that are asymptomatic. Which possibly means that there is something new enough about this virus that most younger people have not already been exposed but also means that older people have been exposed to a similar virus in the past.
As can be imagined most people being examined are those with symptoms but now studies and reports are coming out that show what affect this virus is having on asymptomatic carriers.
Here are some of those findings:
1) Those that are asymptomatic have similar if not more of the virus than those that show symptoms. They have known this for a while.
2) Asymptomatic carriers shed the virus longer that those that show symptoms. Those with mild symptoms shed the virus less that those with more severe responses.
Average viral shedding after infection
Asymptomatic - 19 days
With Symptoms - 14 days
3) Those with symptoms have a higher count of virus antibodies after recovery than asymptomatic carriers. In fact it appears that asymptomatic carriers may have an even higher chance of getting the virus in the future.
4) Unlike SARS and MARS where the immunity was a year or longer neutralizing antibodies in those that recovered Covid-19 start decreasing as quickly as six weeks.
5) A percentage of those that are asymptomatic have lung tissue damage. Of the 76 passengers on the Diamond Princess who were asymptomatic and had CT scans nearly half had lung tissue damage typical of coronavirus infection.
It appears the main difference between those that are asymptomatic and those that have symptoms are the results of the body fighting the disease i.e. fever and inflammation and NOT what the virus is actually doing to the body. Another study showed that 66.7% of asymptomatic individuals had abnormalities in one lung and 33.3% had abnormalities in both lungs.
So now lets look at the Spanish flu
As many probably know there were several waves of the Spanish flu and that young adults and children were especially vulnerable. The first wave started in the United States in the March 1918 through July and then the second wave started in August 2018 with the most deadly month being October. The third and fourth wave was more isolated but the third wave was still more deadly than the first.
The thing to look at here is the first two waves:
First Wave: Deadly for those that were sick and elderly. Most adults that were affected had normal flu symptoms. Younger people were almost not affected.
Second Wave: Most that had the flu during the first wave were immune in the second phase. Those that were affected were primarily the young.
There are a lot of theories about how the virus spread and why the second wave was so devastating to young people but all of the theories were based very limited understanding on viruses in particular and even now our experts are somewhat baffled at the ability to be asymptomatic and have the disease.
For example, people thought that soldiers were a group that was especially vulnerable because of their environment but if you look at it through the lens of today you can make the case that they were because:
1) They are more than likely young adults
2) There was no limited social distancing
3) They were not immune in the second wave because they either weren't exposed to or they were asymptomatic during the first wave.
In conclusion we have limited understanding about the affects of a virus on individuals who have no or limited immunity to the virus because most of the viruses that we are exposed too aren't new or different enough to for the bodies defence mechanisms to not identify and react.
Most importantly we don't know what affect the next wave will be on those that were asymptomatic in the first wave. We know there is a chance that their lungs will already have tissue damage and other possibly cardiovascular issues.
The second wave of the Spanish flu may have nothing to do with initial lack of symptoms in young people during the first wave but the similarities should be noted and reflect our decisions on how we talk to our young people about just how immune they are to Covid-19 and what decisions we make before there is a vaccine available.
Finally, the second wave of Covid-19 is almost a certainty because of the limited time frame of immunity shown in those that have recovered as well as the limited immunity if any of those that were asymptomatic initially. If this runs a similar course as the Spanish flu we will see infections (with symptoms) in younger, initially asymptomatic starting in as early as August or September. For those young people that were never initially infected they will get a pass until the next wave or hopefully there is a vaccine by then.
Reference link:
https://www.nature.com/articles/s41591-020-0965-6
In addition to the OP, here’s a link to a good summary of the two recent Nature articles, focused on antibodies and “shield immunity” :: https://arstechnica.com/science/2020/06/immunity-to-covid-19-may-wane-just-2-3-months-after-infection-study-suggests/
Very useful info.
Surprising to see lung damage present in those who were asymptomatic - and concerning.
I'm not surprised at all but yes am very concerned that young people, including young children, are not "immune" to COVID-19 but rather just. . . asymptomatic. We now know this is basically a hemorrhagic fever. No symptoms doesn't necessarily mean nothing happened. Liver damage, for example, is largely asymptomatic until you die a horrible death. Strokes are asymptomatic until they're not. We still don't know the extent to which exposure to COVID-19 impacts mortality in the asymptomatic.
It's likely I'm overreacting, but that's how I deal with something we know little about. As far as I'm concerned, America could be playing one hell of a game of Russian roulette with its population.
I think it is especially important for those of us with children and young adults of which I have two to realize that symptoms are the caused by the body fighting the virus i.e. fever, coughing, inflammation, etc. and that if your child is/was asymptomatic the virus is still there and potentially doing damage. Or if the bodies immune system never fought the virus - is it still there in the cells?
The other issue we need to think about is the next wave or whenever the limited immunity falls off will the younger people still be asymptomatic or will it be like the 1918 second wave.
As I've posted in other threads, my 34 year old cousin had a covid induced stroke. She didn't know she was sick at all until she was tested at the hospital.
She's doing PT and recovering at home after spending a week in the hospital.
She isn't fat, doesn't smoke, isn't a heavy drinker, and has no underlying health issues.
dumb question (not a doctor nor work in the health industry), but is the lung damage permanent, or does it heal? Too early to tell?
Per John Hopkins : Recovery from lung damage takes time, There's the initial injury to the lungs, followed by scarring. Over time, the tissue heals, but it can take three months to a year or more for a person's lung function to return to pre-COVID-19 levels.
This is where we need to be very careful with athletes that have even been asymptomatic - I would argue that all athletes should get a CT Scan before starting training.
Being an M.D. myself, why would a ct help ? By the time something shows it should have been detected by nasal swab days before
I think he probably meant that if someone tests positive but is asymptomatic, a CT scan (at the very least an x-ray) of the lungs should evaluate for tissue damage before allowing the athlete to participate.
Depends on the extent of the damage, but you shouldn't worry too much about it, especially if patients haven't experienced any symptoms. NPR article about this study goes on to explain the CT scans and says the "damage" or these ground glass opacities can be just a little bit of fluid in the lungs or inflammation and not necessarily scar tissue or long term damage.
My first thought when reading this was: does this happen with other pneumonia causing viruses like common cold coronaviruses that also have mild or no symptoms? We know they can cause severe pneumonia and death (there are thousands of such cases each year) but we don't even have tests for those viruses and certainly don't give CT scans to people with colds. But we're testing and studying covid like we've never tested a respiratory illness before.
And sure enough, there was a comment on that in the NPR article:
"Still, Taylor-Cousar [pulmonologist in Denver] cautions that researchers are studying the new coronavirus more intensively than they've studied other respiratory ailments. "Usually if someone is asymptomatic [with a common cold or flu virus], we would never even see them at all," she says, "and we would never think to get a CT scan on them." So there's no comparable data to say whether the lung abnormalities are specific to asymptomatic coronavirus carriers, or common among respiratory viruses."
So it's likely nothing to freak out about. I think the far scarier thing about the study is that these people can be spreading it to more vulnerable people for so many days, not the mild effects it's causing to lungs in asymptomatic carriers.
* second wave started in August 2018. meant 1918
I feel like the word "asymptomatic" implies certain incorrect assumptions when what we are really talking about are "non-obvious" carriers of the disease. I don't think we can call someone with covid lung damage "asymptomatic" - lung damage is clearly a pretty nasty symptom.
Many covid carriers are also simply "pre-symptomatic" (symptoms will manifest later) or only mildly symptomatic (mild cough or low fever that's somone might easily shrug off as a minor cold).
So the bottom line is that covid is often carried by people who don't even know that they are sick. These unaware carriers then unknowingly spread the disease to others.
I think that is a big part of why we are seeing more emphasis being placed on widespread use of masks, since that helps unknowing carriers from spreading the disease to others. That theory looks like its starting to be confirmed by data from countries where widespread use of masks is prevalent.
I think the use of asymptomatic in this case means that the individual doesn't sense any symptoms. Whereas a doctor via a CT scan or other method would see the scarring of the lungs as a sign or manifestation of the disease.
Masks should definitely be worn - the thing that needs to change with these recent findings is the idea that "I am young this will not affect me even if I get it" mentality.
The first wave started in the United States in the March 1918 through July and then the second wave started in August 2018 with the most deadly month being October.
Shit, that was a long time wait before the second wave.
Seriously, I'm not sure how much predictive value an epidemic from a century ago, involving a genetically different virus, has for us now. It seems like the same people who are adamant that "this isn't the flu!" are expecting it to behave just like flu (or at least, like the flu behaved 102 years ago), which is a curious bit of cognitive dissonance. Coronaviruses are a different animal and we don't really know what to predict. One potential positive is that this one seems to mutate relatively slowly.
Not trying to make the point that the two viruses are the same, though there are some similarities. It's more about how our body reacts to viruses. I was going to cover this but didn't want to write a book.
The reason that I bring up the 1918 flu is that it could vary well be that the same thing happened then in regards to young people being at first asymptomatic and barely even affected to then only get severely affected in the second wave. And believe me I hope that it won't because we are not at all prepared for that scenario right now.
But conversely, people who insist that "it's the flu" don't think of comparing it to the version of the flu that killed tens of millions around the world over the course of a couple of years. Which is also "a curious bit of cognitive dissonance."
Influenza, or the " flu" , is a class of viruses that are quite variable in their effects. The Spanish flu was different in the rapid manner in which it killed victims, often on the first day of symptoms with hemorrhagic pneumonia,
H1N1 flus tend to be more damaging than others. A more than B types.Influenza is interesting in that its genome is generally known and it is a large virus with many complicated genes. There are several common areas which could be targeted for a vaccine, and there is a researcher who is targeting over 30 of these loci to make a universal vaccine given every 5 to 10 years
Corona viruses tend to be cold type viruses without a lot of effect outside the nose and respiratory tract. Unfortunately the body does not consider them a big threat and antibody immunity wanes relatively quickly after infection ( not usually an issue since they don't stick around more than a few months ). If that is the case, even when a vaccine is available the immunity may not last and we may need regular boosters
If this is true of asymptomatic carriers "it means that your immune system does not recognize the virus and didn't fight it in the first place" then how are their bodies getting rid of the virus?
And I know fever and most illness symptoms are immunte responses to the pathogens and not the pathogens themselves but wouldn't damage to the lungs cause some symptoms, like shortness of breath or decreased blood oxygen levels?
I think this is a great question. There's one particularly scary possibility which is that you get long-term asymptomatic carriers who are highly infectious but move around in society because, with no symptoms, they don't realize anything's wrong. That is more or less a description of the classic "Typhoid Mary" case. Basically, the body just adapts and tolerates the pathogen without removing it.
But as far as how it could be cleared, there are still innate/non-specific immune responses working on killing viruses but no 4-alarm fire being declared with the lymphocytes. That makes clearing an infection very, very slow... but the virus is just replicating, budding, replicating, budding, probably until the last of the infected cells are found and destroyed.
Otherwise, the body just learns to live with a lot of viral particles just floating around and a certain number of infected cells churning them out in a kind of equilibrium/stalemate. That's not to be confused with the latent stage of a virus like HSV or HIV, which are hiding (though I should point out that there is at least one theory that the typhus bacteria in Typhoid Mary's case might have actually adapted to hiding out in one type of immune cell long term, but it's just a guess).
Got it. And that would explain how it could cause something to happen to the lungs. But it seems like that "damage" is mild enough to not even cause symptoms in these cases? i.e the equilibrium is reached at a point where the body isn't even phased?
I see now this is what you were talking about after your most recent post as it relates to these "super spreaders." Makes testing, tracing and isolating that much more critical knowing these people are walking around.
I had the same question. I’m also curious if not all asymptomatic people are equal. Does viral shedding volume necessarily correlate with contagiousness? Also, is it possible that some “asymptomatic“ people do have an immune response that is so mild they don’t notice (fever of 99 for example). I’m also curious on the ramifications of “decreasing antibodies” after 2 months. Does this mean that a person is no longer able to leverage the antibodies after 2 months, or longer (how much of a decrease makes a difference and what is the rate of decrease)? Does this timeline get extended if a person with antibodies is exposed again (does the 2 month clock start over)? What does this mean for a vaccine? Does this mean a vaccine will need to be reapplied every 2 months?
I know there are questions on why the outcomes for kids <15 yrs old seem to be so different and whether they transmit the disease as prolifically as adults (good commentary in this article). Have there been scans of recovered asymptomatic kids showing the kind of lung damage you reference above?
It’s like the more we learn the more questions I have...
The answer is we don't know yet and studies on asymptomatic carriers are only just starting. The answer could be that they don't get rid of the virus - it's latent in the cells. As far as the symptoms from damage I agree you would think so but I'm not sure how much the scar damage would be noticeable for those that aren't say athletes especially if our T and NK cells don't recognize it as pathogen - I'll leave that up to any medical professionals that care to comment.
Unlike SARS and MARS where the immunity was a year or longer neutralizing antibodies in those that recovered Covid-19 start decreasing as quickly as six weeks.
This begs the question, if immunity is short-lived, then what difference would a vaccine make?
I suggest you read the diary series by Sopwith. Second from top, specifically about what immunity means.
One more question on this concept:
“First, being asymptomatic to a virus does not mean that you fought the virus off and your body did so a great job that you had no symptoms - on the contrary - it means that your immune system does not recognize the virus and didn't fight it in the first place.”
Isn’t one of the ways in which asymptomatic infections are identified through antibody testing? If someone has antibodies doesn’t that indicate they did have an immune response? Which means their immune system did fight the virus? What am I missing here?
If there was an antibody response against the infection, that's definitely a specific immune response, however minimal. But in the study the OP cited and probably most studies, they're looking at active cases with positive RT-PCR tests.
The one caveat about this and similar studies is that they're looking only for circulating antibodies in the plasma. That leaves out the possibility that after the circulating (i.e., free) antibodies fade out, memory B-cells are still hanging around waiting for another infection. Immune memory is based on the presence of long-term cells, not antibodies. When antibodies are detected for a year-plus (SARS for example), it's probably because there are still memory cells differentiating into "plasma" cells that churn out antibodies (there's an explanation of this in Part III of the Covid Sharpies post). But memory without much circulating antibody can still exist if the memory cells stay as memory cells and don't differentiate without another viral challenge.
The bottom line is that the absence of antibodies after a few months doesn't necessarily mean the immune system has "forgotten" the virus. We just don't know and can't easily test for it in the lab. That's going to require real-world data over the next year, especially once the vaccines roll out. If too many people aren't having any immune response to the vaccines, we've really got a problem. But this paper doesn't necessarily suggest that's going to happen, it's just flagging a potential weak spot (half-life of specific antibodies) we may need to account for.
Thank you, great explanation.
Sopwith is the man!
Came across this small study that's kind of interesting suggesting that people with headache and anosmia had less severe disease. I've had a couple of patients who have had the anosmia symptoms and have done pretty well. https://www.mdedge.com/neurology/article/224253/headache-migraine/headache-may-predict-clinical-evolution-covid-19?ecd=wnl_evn_200622_mdedge_8pm&uac=12629DK&utm_source=News%5FMDedge%5FeNL%5F062220%5FF&utm_medium=email&utm_content=Headache%20may%20predict%20clinical%20evolution%20of%20COVID%2D19
Good post. I like to consider the entire environment if possible and suggest comparing to Histoplasmosis which is the most common endemic fungal infection in North America that affects the lungs. Each year, up to 250,000 people in the U.S. are found to have histoplasmosis. (American Thoracic Society)
For those of us that have been around a few years in the state of Michigan, one study found that almost two thirds of us have some lung scar tissue due to histoplasmosis. I researched this last fall after breathing barn dust filled with bat droppings. I calmed down once I realized it was almost a certainty that I had previous exposure.
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