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Medicine Science

Experts Are Puzzled Over Why the Coronavirus Lingers in Some Asymptomatic Patients For as Long as 40 Days (latimes.com) 218

Shashank Bengali, reporting for Los Angeles Times: By his second day in the hospital with COVID-19, Charles Pignal's mild cough and 102-degree fever had disappeared. Bored and "bouncing off the walls" of his room in the isolation ward at Singapore's National Center for Infectious Diseases, he felt like he could go out and play a set of tennis. The 42-year-old footwear executive told his mother on the phone, "I'll be out of here in a couple of days." But Pignal would test positive for the coronavirus for five more weeks, despite developing no further symptoms. He wasn't released until the 40th day after he first fell ill, when he finally tested negative two days in a row. Cases like his are coming under increasing scrutiny as medical researchers worldwide puzzle over why the coronavirus -- which typically lasts about two to three weeks in the body -- appears to endure longer in some patients, even relatively young, healthy ones.

With studies showing that asymptomatic patients can transmit the SARS-CoV-2 virus, understanding how the virus leaves the body is among the most urgent mysteries facing researchers as governments in the United States and across the world begin to reopen their economies. Although studies show that the average recovery time from COVID-19 is two weeks, and nearly all patients are virus-free within a month, "less than 1% to 2%, for reasons that we do not know, continue to shed virus after that," said Hsu Li Yang, a physician specializing in infectious diseases at the Saw Swee Hock School of Public Health at the National University of Singapore. In recent weeks, China and South Korea have reported that some patients who had recovered from COVID-19 tested positive again in follow-up visits. In extreme cases, patients in the Chinese city of Wuhan, where the outbreak began late last year, reportedly tested positive 70 days after recovery. Doctors in both countries said they didn't believe the patients had been reinfected, a worrisome possibility because of its implications for building widespread immunity to a disease for which there is no vaccine. They also had no evidence that the patients had infected others.

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Experts Are Puzzled Over Why the Coronavirus Lingers in Some Asymptomatic Patients For as Long as 40 Days

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  • by DeAxes ( 522822 ) on Tuesday May 05, 2020 @01:43AM (#60023314)

    One of the known issues with PCR tests is that it can't distinguish between Live and Dead cells. So, the Covid19 cells detected could be dead virus, including leftover pieces of the virus that the body already killed off.

    • by kot-begemot-uk ( 6104030 ) on Tuesday May 05, 2020 @02:06AM (#60023350) Homepage
      The field tests also cannot distinguish between viral RNA load and something which has managed to incorporate into the host genome.

      It is possible to do that in a proper lab where you wipe the DNA slate clean with DNAse before reverse transcription of the RNA to amplify it via PCR. A basic rapid test does not do that. It just shoves the sample into the machine and assumes the only thing which will be amplified is whatever was reverse - transcribed.

      • by Molron ( 5522682 ) on Tuesday May 05, 2020 @05:14AM (#60023646)
        Retroviruses like HIV do integrate into the genome, but coronavriuses do not: they lack a reverse transcriptase to convert their RNA genome into DNA so that it can be inserted into the host genome. Your comment doesn't make sense here.
        • by rtb61 ( 674572 )

          It is down to the genes of the individuals involved. Just like some people run faster than others due to genetic advantages, so the reaction rates of their immune systems differ. How fast and how much their immune systems react to an infection based upon the degree of infection, will vary from individual to individual. So a virus not causing much harm, is largely ignored by some immune systems, simply because the negative reaction is insufficient to generate a immune response to tackle the infection, so the

        • Still, the virus could stay in infected cells. It's the same problem as if it is in the DNA, it just sits somewhere else in the cell.

          I guess infected cells can still release the virus long after the infection has worn off, but the immune system will kill most viruses before they can leave the body.
    • I'd be pretty pissed if they messed up testing and kept me locked up for 40 days. You would think after the symptoms went away, they'd try a test that was more conclusive...
      • More conclusive tests involve directly detecting the viral particle. That's far more difficult than antibody or PCR tests. It does demonstrate the weakness in the argument "more testing!" because antibody tests cannot, at least in some cases, tell the difference between COVID-19 and some other coronaviruses, and since the common cold hasn't disappeared during the pandemic, you could potentially distort infection rates higher.

        The more sensible thing to do is to randomly pick people from the general populatio

      • by dcw3 ( 649211 )

        I'd be pretty pissed if they messed up testing and kept me locked up for 40 days. You would think after the symptoms went away, they'd try a test that was more conclusive...

        You have to think about how this evolved. A couple months ago, they didn't know how long it took someone to become symptomatic after initial exposure. We kept hearing wide ranging numbers. And even then, if you were asymptomatic, how long could you be spreading the virus? Hindsight doesn't help in the early stages.

    • by fintux ( 798480 )
      Yes, knowing which one the shed particles are, is the million dollar question. Or actually possibly the trillion dollar question...
    • It doesn't surprise me since even a pawpaw can test positive: https://www.nzherald.co.nz/wor... [nzherald.co.nz]
    • Why don't they test the ability of a sample to infect in vitro on a cell culture? They are testing medicines in vitro so they must have the capability.

      • Afterwards how do you know what you've cultured. You still have to test for COVID19. Otherwise it could be a different virus for detecting the lung. The process of culturing is not for identifying infections, it's to amplify the infection so that you can more readily identify it.
      • Virii do not have cells. They are just DNA/RNA, protien and lipids.
      • It is debatabkee whether virii are alive. There are certainly no distinctions between dead and alive.
    • As the lungs open up again after a serious case of covid19 they release a lot of corona virus snippets which will indeed be detected as virus.
      This case is interesting in a different manner though: the patient is asymptomatic.

    • Comment removed based on user account deletion
    • by hey! ( 33014 )

      Well, it'd be more accurate to say that PCR can't distinguish between viable non-viable virus, since viruses don't have cells and don't have their own physiology to be alive with.

      Even so, that's unlikely to be the cause. Why would the patient's body be shedding viral RNA for weeks after the infection cleared? Why would it linger longer than any other virus's RNA or DNA? Anyhow, if it were the case that the body was shedding inactive virus this'll be cleaned up right away. Someone will do a Vero cell cultu

  • by Camel Pilot ( 78781 ) on Tuesday May 05, 2020 @01:49AM (#60023328) Homepage Journal

    China and South Korea have reported that some patients who had recovered from COVID-19 tested positive again in follow-up visits. In extreme cases, patients in the Chinese city of Wuhan, where the outbreak began late last year, reportedly tested positive 70 days after recovery.

    I thought this was due to the imprecise method used to test for COVID-19. The test looks for a polymerase chain reaction which cannot distinguish between genetic material from a current active infection or just virus debris or inactive fragments (ie. dead soldiers) that can linger in the body long after a person recovers.

    • And the reason for that is that early on, it was preferable for a test to fail positive, rather than fail negative. That is, it was preferable for a test to show positive for infection when the person actually was not infected or had already recovered from the virus; than for the test to show negative for infection when the person actually was infected. If you mistakenly quarantine someone who is not infected, it's just inconvenient for that person. if you fail to detect and quarantine someone who is inf
    • Wouldn't the leftover junk get flushed out pretty quick?
  • My guess... (Score:5, Interesting)

    by Kaenneth ( 82978 ) on Tuesday May 05, 2020 @02:07AM (#60023352) Journal

    With sensory loss (taste/smell) being one symptom, maybe it's getting into nerve cells which have a much slowerr growth cycle; Rabies/Shingles can linger for a long time.

    https://www.ninds.nih.gov/diso... [nih.gov]

    "Shingles is the reactivation of a viral infection in the nerves to the skin that causes pain, burning, or a tingling sensation, along with an itch and blisters in the skin supplied by the affected nerve. It is caused by the varicella zoster virus[1], or VZV—the same virus that causes chickenpox. When the itchy red spots of childhood chickenpox disappear, the virus remains in a dormant state in our nerve cells, ready to strike again in later life. This second eruption of the chickenpox virus is called shingles or herpes-zoster. "

    https://www.cdc.gov/rabies/tra... [cdc.gov]

    "From numerous studies conducted on rabid dogs, cats, and ferrets, we know that when the rabies virus is introduced into a muscle through a bite from another animal, it travels from the site of the bite to the brain by moving within nerves. The animal does not appear ill during this time.

    The time between the bite and the appearance of symptoms is called the incubation period and it may last for weeks to months. A bite by the animal during the incubation period does not carry a risk of rabies because the virus has not yet made it to the saliva."

    Covid-19 could be an ongoing nightmare for even the 'asymptomatic' people for months, years, or even decades to come.

  • by Anonymous Coward
    I'm curious to see if this virus does a number on budding cancer cells and makes the world cancer free for a few years.
  • by Viol8 ( 599362 ) on Tuesday May 05, 2020 @03:38AM (#60023494) Homepage

    And occasionally pops up again as shingles when you're physically a bit low. Viruses have had a billion years of evolution behind them to become extremely adept at what they do.

    • by De_Boswachter ( 905895 ) on Tuesday May 05, 2020 @04:46AM (#60023616) Homepage
      Chickenpoxviruses are herpesviruses with over a hundred of genes, the majority of which is dedicated to life-long immune evasion with many redundancies. These have indeed evolved over hundreds of millions of years--co-evolved with immune systems would be a better description. SARS-CoV-2 literally didn't exist on this planet less than half a year ago. Also, coronaviruses in general have ten times less the genetic payload and are therefore far less likely to persist to linger that long. I'd say 40 days is an outlier.
      • "SARS-CoV-2 literally didn't exist on this planet less than half a year ago." - There is nothing new under the sun. If you believe that Covid-19 is really new, then I have a nice beach front arctic property I can sell you.
    • Hosts have been around for those billions of years too. And without living hosts, the virus would have perished. The hosts are very adept at what they do.

    • Viruses have had a billion years of evolution behind them to become extremely adept at what they do.

      So have we.

  • Maybe it wants to meet new people.

  • This is the same problem they were researching in Wuhan in 2019, trying to find out why coronaviruses sometimes linger in bats asymptomatically or for a prolonged duration.
  • For the next wave.

  • and I will wipe from the face of the earth every living creature I have made...
  • by DontBeAMoran ( 4843879 ) on Tuesday May 05, 2020 @10:59AM (#60024346)

    Right now, the whole world is upside down. And for that, Australians are grateful.

  • If you think about it, a big element is the body response to the virus when it comes to symptoms. So, what if the body doesn't respond to the virus, no symptoms show up, even though it is there. For those with a strong immune system, the body may stamp the virus out, for those with a weak immune system, they will show symptoms and it will linger on for a longer period of time.

    So, what about those in the middle, not terribly strong or weak? The symptoms come from a reaction that the body has to the vir

  • by omfglearntoplay ( 1163771 ) on Tuesday May 05, 2020 @02:32PM (#60025158)

    Not that it is directly related, but it isn't unheard of for viruses to hang out dormant in the body for decades. It seems very plausible for some people to naturally "shed" viruses after being sick for weeks. Maybe they do it for all colds and whatnot, and only now with the crazy testing is it being discovered.

The biggest difference between time and space is that you can't reuse time. -- Merrick Furst

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