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Mon Mar 30, 2020, 10:36 AM

Covid patients can remain infectious following recovery.

The paper to which I will refer is this one from scientists in China, where they have the most long term knowledge of this disease: Chang, Mo, Wang et al., Journal of Respiratory and Critical Care Medicine, https://doi.org/10.1164/rccm.202003-0524LE.

It is a small study and its statistical power is unclear, but in the interest of safety, it may be wise to consider it.

The world's scientific publishing community has made all Covid related papers open sourced, and this paper is no exception.

Time kinetics of symptom onset, duration of symptoms and viral clearance is described
in Table 1. The viral detection test was performed upon clinical presentation and repeated
every other day until the patient tested negative. The negative test was confirmed again
the next day. Upon confirmation of the negative test, the patient was asked to quarantine
at home for the next two weeks with a follow-up visit to the hospital after one week to
confirm the viral negative status. The incubation periods were estimated based on the
history of the patientís travel or potential exposure. Our data show an incubation period
of 5 days (IQR 1-6 days) among the patients (except for patient 12 who had no specific
exposure). The mean duration of symptoms was estimated to be 8 days (IQR 6.25-11.5).
Most importantly, half (8/16) of the patient remained viral positive (a surrogate marker of

shedding) even after the resolution of symptoms (Median 2.5 days, range 1 to 8 days).
Some of our patients had other comorbidities, which included diabetes (2/16) and
tuberculosis (1/16), both of which did not affect the time course of the disease. Similarly,
the clinical course for the 3-year-old male did not significantly differ from the rest of the
patients.


Be safe and healthy.

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Arrow 24 replies Author Time Post
Reply Covid patients can remain infectious following recovery. (Original post)
NNadir Mar 2020 OP
SWBTATTReg Mar 2020 #1
NNadir Mar 2020 #2
SWBTATTReg Mar 2020 #3
NNadir Mar 2020 #5
SWBTATTReg Mar 2020 #8
WhiteTara Mar 2020 #9
NNadir Mar 2020 #11
WhiteTara Mar 2020 #14
Igel Mar 2020 #16
NNadir Mar 2020 #18
defacto7 Mar 2020 #12
NNadir Mar 2020 #13
WhiteTara Mar 2020 #15
defacto7 Mar 2020 #20
WhiteTara Mar 2020 #4
SWBTATTReg Mar 2020 #6
cstanleytech Mar 2020 #23
NNadir Mar 2020 #7
defacto7 Mar 2020 #10
Igel Mar 2020 #17
NNadir Mar 2020 #19
Warpy Mar 2020 #22
SWBTATTReg Mar 2020 #24
Warpy Mar 2020 #21

Response to NNadir (Original post)

Mon Mar 30, 2020, 10:43 AM

1. Ehh what?

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Response to SWBTATTReg (Reply #1)

Mon Mar 30, 2020, 10:49 AM

2. If someone has had Covid and has recovered from it, they can still be contagious. n/t.

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Response to NNadir (Reply #2)

Mon Mar 30, 2020, 11:00 AM

3. Thanks, I got this drift, it was just the article was kind of a spaghetti word salad to me...perhaps

Last edited Tue Mar 31, 2020, 07:47 AM - Edit history (2)

it was only to me, and I apologize, I mean no disrespect. Thanks so much for clarifying.

Be safe.

Be interesting to see that if the body does defeat the CV the first time around, then obviously when CV reappears again, is it another new infection from outside sources or is it from a hidden reservoir within the body where the virus is 'hiding'? If the host defeated the CV the first time around, then how is the new wave of CV infection getting by the now trained antibodies?

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Response to SWBTATTReg (Reply #3)

Mon Mar 30, 2020, 11:29 AM

5. No problem. I'm not always very good at translating stuff to non-scientists.

It is very rare for a viral infection to recur in a recovered patient, since recovery implies that the patient has developed effective antibodies and is resistant to further infection.

A huge exception to this case is HIV infections, where the immune system itself is under attack.

This said, viruses can and do mutate rapidly owing to their very primitive and error prone replication system. In HIV, where the immune system is itself compromised, and where non compliance issues (skipping doses of antiviral drugs) a number of mutations have been shown to arise, and patients can develop drug resistant strains.

There are, in some disease models, cases where "reservoirs" are not accessible to antibodies, but they are not, to my understanding, typically viral diseases. This scenario is well known in some types of cancer diseases, where cancer cells are localized in an area to which a treatment drug is not able to penetrate.

I have read papers indicating that the virus may have originated in pangolins - ant eaters - and became "humanized" when the virus developed in humans. I have a post in this section discussing this scenario, but it may be, as you say, "spaghetti."

The operative point here is that if you know someone who has recovered from Covid-19 it may not be safe to assume that they cannot infect a person.

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Response to NNadir (Reply #5)

Mon Mar 30, 2020, 11:36 AM

8. Thanks so much. A good article. Be safe and healthy. NT

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Response to NNadir (Reply #5)

Mon Mar 30, 2020, 11:48 AM

9. thanks for the info. Combined with the statement

that I saw on DU this morning, you may still be able of infecting others after you have recovered. This sounds like an apocalytic illness. Or am I catastrophizing this?

I may never leave my house again.

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Response to WhiteTara (Reply #9)

Mon Mar 30, 2020, 12:02 PM

11. There seems to be an endpoint for being infectious. It is NOT forever.

I strongly suspect, based on general knowledge, that there are many people who have had cases so mild that they didn't notice it before developing antibodies.

I had a joke thread over in the DU lounge about the fact that in studying this disease, I realized that I'm a mutant.

Trapped in the house with me, I feel for my wife and sons listening to me brag about my ACE2.

Although there is zero serious evidence that my mutation has any effect on Covid-19, it does seem likely to me that there are people who are genetically immune. I recall reading somewhere that it is believed that the black plague in Europe and Asia in the middle ages did leave a genetic signature in humanity, simply because people having a specific mutation did not die from the plague, and thus were able to reproduce.

What the world community is working to do is not to prevent large numbers of people from getting the disease, but to try to time the disease in such a way that the health systems are not entirely overloaded. This would be a bad time to get the disease in say, New York City, but when a large subset of the population develops immunity simply as a result of having had the disease and recovered, transmission will be less likely and the opportunities for treatment larger.

We all need to be careful and vigilant, but that said, we should recall one of greatest Presidents in saying, "The only thing we have to fear is fear itself." If we are wise, we will recover.

Stay safe, stay calm.

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Response to NNadir (Reply #11)

Mon Mar 30, 2020, 01:30 PM

14. Thanks. That staying infectious AFTER getting well

is concerning, but of course, nothing is forever. Fortunately, I can stay home and self-isolation is pretty much a way of life. I'm planning on being isolated for at least a year. I hope I use the time wisely and earnestly work on my practice.
Thanks for the great answers without snark.

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Response to NNadir (Reply #11)

Mon Mar 30, 2020, 01:54 PM

16. This was a fluke--it doesn't happen often.

And there's this recurring suspicion that what granted partial resistance to Y. pestis is the same quirk that enables Graves disease.

In which case it's similar to sickle cell--yeah, you get a partial pass on something that's bad, but you pay for it. If the bad thing is around a lot, it's worth the price; if the bad thing goes away, you're still stuck with the bill.

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Response to Igel (Reply #16)

Mon Mar 30, 2020, 02:27 PM

18. Well, it's very obvious that disease syndromes with the mortality rate of Black Plague are rare.

So it's a good thing it's rare, but I think "fluke" is a poor choice of wording. Natural selection is not a "fluke."

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Response to NNadir (Reply #5)

Mon Mar 30, 2020, 12:17 PM

12. You said there are conditions where mutations are known to arise.

We know about the possible effect of improper antibiotic use on the creation of resistant bacteria but I was wondering if these virus mutations from anti-viral misuse can remain specific to the patient and unlikely to shed beyond the individual. Do you know if this occurs? It's a curiosity that some people and/or their invader are resistant to medication when others are not. Any insight?

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Response to defacto7 (Reply #12)

Mon Mar 30, 2020, 01:01 PM

13. The mechanism by which resistance arises in bacteria, and in viruses is similar.

It is actually most widely observed in viruses, since, while bacteria replicate rapidly, viruses to do even faster.

It's all about the Nietzschean "That which doesn't kill you makes you stronger."

Early in the AIDS epidemic a large class of AIDS drugs were developed in a class of drugs known as Protease inhibitors. If one took one of these, and most patients started with just one of the available drugs, they were effective at deactivating the virus above a level we call a "trough." The dosing schedule is designed so that patients will have physiological levels well above this trough. But if one forgot to take a dose, one could fall below this trough.

Most mutations result in inoperative viruses that cannot function. But in rare cases there are mutations that allow for a functional virus that has a mutation allowing for continual functionality and improved resistance to a drug.

Consider that viruses replicate on a scale of billions of viral particles a day. Suppose, because the machinery of the virus replication is primitive, that 100 million are mutants, most of which are no longer functional. But in that hundred million there are say, 500 that are functional, and of these, there are 10 that are functional and have developed some level of resistance to the drug. As the amount of the drug goes lower, many of the viruses are rendered inoperative, but those 10 have enough resistance to overcome the effects of the drug. There is nothing to stop these survivors from infecting cells, since they are functional. If they are allowed to do so and are not killed, all of their progeny, except those damaged by poor replication, will come to dominate the viral load by natural selection.

We have fully sequenced the target HIV protease, but as we observed patients showing resistance, we found sequences that were different than those for which the drug was designed.

Protein sequences are often described by one letter codes representing each of the 20 eucaryotic coded amino acids.

Here is a list, from my files of mutants to HIV drugs:

D30N: Nelfinavir. (Agouron/Pfizer).
M46I/I47V/I50V: Amprenavir (BMS).
L10R/M46I/L63P/V82T/I84V: Indinavir (Merck)
M46I/L63P/A71V/V82F/I84V: Ritinovir (Abbott).
Saquinavir: G48V/L90M (Roche)

D30N means that at residue 30 in the protease, an aspartic acid (D) has been replaced by an asparagine (N). (This old stuff by the way, dating back well over a decade.) Notice that in some cases, indinavir and retinovir, there are multiple mutations.

This fast evolution is driven by high replication rates coupled with large replication inaccuracy. Now it may be that a particular single mutation does not confer full resistance, but allows for enough resistance, to allow for the virus to "survive" when the level of the drug falls below a certain level because the patient skipped a dose, or because the drug was not available because of costs or logistics.

Since sub-saharan Africa is an AIDS hotspot, and because the drugs were sometimes only sporadically available, this made for rapid mutations. If a patient does not transmit these variants to another person, it stops with that person. But that is not always observed, as we know.

I hope this helps explain the issue.

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Response to NNadir (Reply #13)

Mon Mar 30, 2020, 01:38 PM

15. you are a wealth of information

Thanks

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Response to NNadir (Reply #13)

Mon Mar 30, 2020, 03:50 PM

20. Excellent explanation.

It's all the more clear that denying the virus the means to spread by distancing and sanitary practice is the best way to limit it and survive outside of a vaccine. Although we already knew this by the word of experts, to me it's important to know why that is true and the mechanism by which it is so. This explains a lot. Thanks for your insight.

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Response to NNadir (Reply #2)

Mon Mar 30, 2020, 11:25 AM

4. Have you seen anything about immunity after

the illness? I saw one small blurb from China that said you could get the virus again but have heard nothing else.

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Response to WhiteTara (Reply #4)

Mon Mar 30, 2020, 11:34 AM

6. No, the only thing I heard is that you can get CV again, and also heard that once you have, you ...

are immune. I'm hearing from both sides of the fence, and I'm confused (easy to do in my case), I'll see if there's anything new out there, but I keep hearing different things. I thought, like any other viruses, once you get and recover, you're immune, a standard thing. But I just read (in a DU article from China), that you're not safe.

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Response to SWBTATTReg (Reply #6)

Mon Mar 30, 2020, 09:29 PM

23. Perhaps those catching it again either did not fully recover yet or they caught a mutation?

After all the flu mutates constantly which is why we need to take a different vaccine every year so I would not be shocked if we see cases where this coronavirus mutates.

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Response to WhiteTara (Reply #4)

Mon Mar 30, 2020, 11:34 AM

7. I just touched on this case in a response to another post.

Please see post #5.

I want to be clear, however, that I am not an expert in virology and while I am familiar with many diseases as a part of my profession nothing I say can be characterized as authoritative.

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Response to NNadir (Original post)

Mon Mar 30, 2020, 11:59 AM

10. Good info in a pinch.

Even if it's not conclusive there's little room for error. My wife is involved in deciding when it's safe for children to return to school after an illness. Available guidelines vary from place to place, state to state which is awkward and dangerous. We have to err on the safe side. I'll pass this along. Thank you.

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Response to NNadir (Original post)

Mon Mar 30, 2020, 02:01 PM

17. Still doubtful.

Yes, it took longer for what was tested to be cleared.

But what they tested for wasn't live virus.

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Response to Igel (Reply #17)

Mon Mar 30, 2020, 02:50 PM

19. The state of the virus is, if you read the paper, indeterminate.

They explicitly state that their test was PCR based, which is destructive testing.

They offer no information as to whether the virus particles were infectious or not. I would think, that under the circumstances, it would be far superior to be cautious, since with the orange idiot in power, we have seen what an incautious approach based on rote assumptions is.

It is neither "doubtful" or "confirmed" that the viruses are active, but let's put this way: My sister-in-law is recovering (hopefully) from Covid. I will advise my niece and nephew to consider that she may be contagious. If she is not, great. If she is, however, I would be appalled if the outcome were tragic because I stated that this result is "doubtful."

Again it is neither "doubtful" nor confirmed. The world community is racing to understand this virus, and the urgency of the program and the stress under which work is conducted is bound to produce some results that do not stand up to time. But a sane approach is to treat every bit of information as having potential validity until it is shown that it is not valid.



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Response to NNadir (Reply #19)

Mon Mar 30, 2020, 04:52 PM

22. Caution is vital

They already know that SARS persisted in feces for up to 10 months post illness and that this bug shares 80% of its genome with SARS. Whether the persistence of this bug in oral swabs is due to overall persistence or to fecal-oral contamination (which happens more often than any of us would like to admit) is anyone's guess at this point.

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Response to NNadir (Reply #19)

Tue Mar 31, 2020, 08:07 AM

24. Thanks again for all of the information, and I especially wanted to wish your sister-in-law Get ...

Well Wishes.

The DU community of which we all are a part of, I'd like to think, are all wishing and/or praying fervently for her (and of course others) to all recover fully without lasting harm.

Take care.

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Response to NNadir (Original post)

Mon Mar 30, 2020, 04:47 PM

21. Thank you so much for this

It seems a quarantine period of about 3 weeks will be necessary for people who show symptoms. Unfortunately, not everyone who is symptomatic is going to get tested, either through lack of access to health care or because they are working and can't afford to be quarantined.

IOW, this virus is going to be with us for a while because it gets us coming and going, before and after symptoms are apparent.

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