Asymptomatic SARS-CoV-2 Infections - How rare?

[FIREd_2015]

Anything that an asymptomatic person coughs on, breathes on or touches is potentially contaminated and a new source for infection. A study showed that the virus "...was detectable in aerosols for up to three hours, up to four hours on copper, up to 24 hours on cardboard and up to two to three days on plastic and stainless steel. The results provide key information about the stability of SARS-CoV-2, which causes COVID-19 disease, and suggests that people may acquire the virus through the air and after touching contaminated objects."

If a person gets on a subway/train/bus and grabs the stainless steel bar within 2-3 days of when the infected person touched/coughed on the same spot and then touches their face this person can now be infected.

https://www.nih.gov/news-events/news...hours-surfaces

[audreyh1]

Quote:

Originally Posted by NW-Bound Quote: In South Korea, more than 20% of asymptomatic cases reported to the Korea Centers for Disease Control and Prevention didn’t develop symptoms during hospitalization... No symptoms during hospitalization? South Korea has enough hospital capacity to take in infected people with no symptoms? Here, Americans with some symptoms cannot even get tested. What a 3rd world country we are.

Yeah that bit had me scratching my head - why would they be hospitalized if they had no symptoms?

[NW-Bound]

See my subsequent post. It's probably more a quarantine for observation.

[USGrant1962]

Quote:

Originally Posted by FIREd_2015 Anything that an asymptomatic person coughs on, breathes on or touches is potentially contaminated and a new source for infection. A study showed that the virus "...was detectable in aerosols for up to three hours, up to four hours on copper, up to 24 hours on cardboard and up to two to three days on plastic and stainless steel. The results provide key information about the stability of SARS-CoV-2, which causes COVID-19 disease, and suggests that people may acquire the virus through the air and after touching contaminated objects." If a person gets on a subway/train/bus and grabs the stainless steel bar within 2-3 days of when the infected person touched/coughed on the same spot and then touches his face this person can now be infected. https://www.nih.gov/news-events/news...hours-surfaces

To be clear, "detectable" does not mean contagious. Like every communicable disease it takes a reasonable dose to get infected. Every credible source says that spread is mainly person-to-person. But those stainless steel subway grab bars in NYC are probably so coated with the stuff that they are well beyond just "detectable" levels.

[Sunset]

Quote:

Originally Posted by USGrant1962 To be clear, "detectable" does not mean contagious. Like every communicable disease it takes a reasonable dose to get infected. Every credible source says that spread is mainly person-to-person. But those stainless steel subway grab bars in NYC are probably so coated with the stuff that they are well beyond just "detectable" levels.

They why all the warnings not to touch our face ?

If I touch stuff that an infected person has touched, is it ok to touch my face ? lick my fingers ?
I don't think so.

[MRG]

Quote:

Originally Posted by EastWest Gal I agree. Greatest health care system in the world? I think not. Three points: 1. South Korea had a good viral PCR test early on, and did the classic thing epidemiologists do in an outbreak: Do contact tracing and testing. Without testing of asymptomatic people, you cannot determine the rate of asymptomatic infections. I believe South Korea hospitalized all those testing positive, regardless of symptoms, to disrupt the spread of the infection. Here in the USA, we'll get billed for several thousand dollars just for walking into an ER with any problem, however minor, and we don't have the hospital beds to isolate mildly ill people with COVID-19. South Korea did, apparently. 2. It is too early in the pandemic to do testing for asymptomatic infection. The viral PCR test is done on a nasopharyngeal swab, or on sputum when available. Viral PCR test from blood or body fluids is unreliable, with many false negative tests. Countries are now developing serologic testings. Serologic tests cannot identify acute infections, as they test antibody response. In some infections, early antibody tests can be done to identify acute infection (measurable levels of the acute type of antibodies, known as IgM) vs past infection, with the long term type of antibody, known as IgG). These do not provide rapid diagnosis though, and it can take 4-6 weeks or longer to develop detectable IgG levels to a virus. 3. There are other well known infections which are asymptomatic in large numbers of people. One of these is mumps. 50% of those infected never have any symptoms at all, but develop IgG antibodies. However, mumps can cause meningitis or encephalitis, deafness, pancreatitis, orchitis (inflamed testicles) and male sterility, so we have a vaccine to prevent all the bad stuff. Measles, on the other hand, is almost never asymptomatic. Given how quickly the numbers started dropping in South Korea, I suspect we will find that there are a higher number of asymptomatic cases than we have suspected up until now. In the long run, this is a good thing, as "herd immunity" may then develop more quickly than expected. This is just a slightly educated guess. Still, one can hope.

Thank you for sharing. I hope you are correct.

I agree, I think S. Korea jumped on it and used data to be very precise and keep the disruption minimized. That's smart, we probably don't know how smart right now. Hopefully when this settles down we can learn from what works and what doesn't.

[JoeWras]

Quote:

Originally Posted by FIREd_2015 Anything that an asymptomatic person coughs on, breathes on or touches is potentially contaminated and a new source for infection.

Or talks near. This is why I think restaurants need to be closed. Everyone talks over a meal. All kind of stuff is flying onto each other's meals, and then onto the table and chairs for the next patrons. Additionally, speech creates small aerosols that can be breathed in deeply by your table mates or NYC strap hanger neighbors.

Here's an interesting article that puts some science on that, including the cultural differences of loudness of speech. I'm thinking of Italy and their demonstrative speaking:

https://www.nature.com/articles/s41598-019-38808-z

Quote:

Mechanistic hypotheses about airborne infectious disease transmission have traditionally emphasized the role of coughing and sneezing, which are dramatic expiratory events that yield both easily visible droplets and large quantities of particles too small to see by eye. Nonetheless, it has long been known that normal speech also yields large quantities of particles that are too small to see by eye, but are large enough to carry a variety of communicable respiratory pathogens. Here we show that the rate of particle emission during normal human speech is positively correlated with the loudness (amplitude) of vocalization, ranging from approximately 1 to 50 particles per second (0.06 to 3 particles per cm3) for low to high amplitudes, regardless of the language spoken (English, Spanish, Mandarin, or Arabic). ... Furthermore, the results suggest a new hypothesis: that speech superemitters might contribute to the phenomenon of superspreading, in which a relative few contagious individuals infect a disproportionately large number of secondary cases during infectious disease outbreaks

[ERD50]

Quote:

Originally Posted by EastWest Gal ... Given how quickly the numbers started dropping in South Korea, ....

But the deaths have not been dropping. I know they are a lagging indicator (incubation time plus time from incubation to death), but new cases took a sharp drop 22 days ago (March 4th) in SK.

Their new death numbers have had two new highs in the past 5 days, and 4 of 7 past days had as-high-or-higher than the past highs. Five deaths already reported for today (GMT)

These are small numbers ( 0 to 9 daily deaths), but I would think we would see some trend down by now?

https://www.worldometers.info/corona...y/south-korea/

-ERD50

[FIREd_2015]

Came across this story about asymptomatic transmission in the State of Washington from a music rehearsal -

"...Sixty singers showed up. A greeter offered hand sanitizer at the door, and members refrained from the usual hugs and handshakes...Nearly three weeks later, 45 have been diagnosed with COVID-19 or ill with the symptoms, at least three have been hospitalized, and two are dead...Everybody came with their own sheet music and avoided direct physical contact...In interviews with the Los Angeles Times, eight people who were at the rehearsal said that nobody there was coughing or sneezing or appeared ill..."

https://www.yahoo.com/news/choir-dec...023414705.html

[tmm99]

Quote:

Originally Posted by FIREd_2015 Came across this story about asymptomatic transmission in the State of Washington from a music rehearsal - "......Everybody came with their own sheet music and avoided direct physical contact...In interviews with the Los Angeles Times, eight people who were at the rehearsal said that nobody there was coughing or sneezing or appeared ill..." https://www.yahoo.com/news/choir-dec...023414705.html

I am not 100% sure that nobody had any symptoms, but let's say that was the case...

So nobody was sneezing, I get that, but this was a singing rehearsal which means that they were singing and when people sing, they spit a lot. We all have seen singers on TV with background lighting and you see spits flying.

What I want to know is, assuming that there was only one person with the virus there and that nobody changed the seating arrangement from the beginning to end, could this person give her spit/droplets to that many people?

I read somewhere that droplets from a sneeze, etc could be floating in the air up to 30 minutes...

[USGrant1962]

Quote:

Originally Posted by tmm99 Nobody was sneezing, I get that, but this was a singing rehearsal which means that they were singing and when people sing, they spit a lot. We all have seen singers on TV with background lighting and you see spits flying. What I want to know is, assuming that there was only one asymptomatic person there and nobody changed the seating arrangement from the beginning to end, could this person give her spit/droplets to that many people? I read somewhere that the spit could be floating in the air up to 30 minutes...

And sneezing is not a common symptom of COVID-19, nor the flu. If you are sneezing it is probably a cold.

[NW-Bound]

Back on the topic of this thread about asymptomatic infections, I just watched a video shared by Nemo2 on another thread, which was an interview with a South Korean doctor of infectious diseases (with English subtitle). The doctor stated that 20% of the infected never had any symptom.

The above concurs with the data mentioned in the Bloomberg article that EveryLady shared earlier.

[tmm99]

Quote:

Originally Posted by USGrant1962 And sneezing is not a common symptom of COVID-19, nor the flu. If you are sneezing it is probably a cold.

No, that's not the point. What the people there said was that nobody appeared to be sick (no coughing, no sneezing, etc) and that's what I trying to say; nobody seemed sick.

Anyway, the article I read about this before this post didn't have details, but this article does, and the article does explain how the seating was arranged and it also talks about the droplets staying in the air much longer in some cases, etc....

[tmm99]

Quote:

Originally Posted by NW-Bound Back on the topic of this thread about asymptomatic infections, I just watched a video shared by Nemo2 on another thread, which was an interview with a South Korean doctor of infectious diseases (with English subtitle). The doctor stated that 20% of the infected never had any symptom. The above concurs with the data mentioned in the Bloomberg article that EveryLady shared earlier.

This seems like old news now, but if you remember, every passenger and every crew member on Princess Diamond was eventually tested, and around 45% of the people who tested positive were asymptomatic.

They then discovered that around 1/3 of the asymptomatic and light cases did show abnormality in the CT scans of their lungs (which means to me that they were not asymptomatic after all...) and the symptoms of 1/2 of those became more serious later on. I don't know what happened to the 2/3 of the asymptomatic corona patients - maybe their test results turned negative after a while without them ever having any symptoms.

[NW-Bound]

Quote:

Originally Posted by tmm99 This seems like old news now, but if you remember, every passenger and every crew member on Princess Diamond was eventually tested, and around 45% of the people who tested positive were asymptomatic. They then discovered that around 1/3 of the asymptomatic and light cases did show abnormality in the CT scans of their lungs (which means to me that they were not asymptomatic after all...) and the symptoms of 1/2 of those became more serious later on. I don't know what happened to the 2/3 of the asymptomatic corona patients - maybe their test results turned negative after a while without them ever having any symptoms.

Thanks. I was not aware of this at all. The reports are often incomplete and leave more questions unanswered.

[audreyh1]

Quote:

Originally Posted by tmm99 I What I want to know is, assuming that there was only one person with the virus there and that nobody changed the seating arrangement from the beginning to end, could this person give her spit/droplets to that many people? I read somewhere that droplets from a sneeze, etc could be floating in the air up to 30 minutes...

They did move around a bit. At one point the group was gathered around two separate pianos.

https://www.latimes.com/world-nation...choir-outbreak OK, same article just from original latimes source.

To me it would seem like more than one attendee was infected due to community spread and didn’t know it.

I guess singing in public is not a good idea right now.

[JoeWras]

Quote:

Originally Posted by audreyh1 I guess singing in public is not a good idea right now.

First of all, thanks for the article pointer. I thought it was just another pointer to the earlier article. This one has much more information. The article just brushes on the airborne idea. There's little chance that everyone touched a contaminated surface. At least some had to have breathed in some droplets.

Clearly, singing can forcefully expel aerosols. I'll mention again that researchers have been looking at the role speech has in expelling aerosols. Here's a technical paper for the details.

In short, loud talkers expel more. This is why I think restaurants are a big environment for transmission. Most are so damn loud now we have people yelling at each other, spitting in their faces and on their meals. (Although it is unseen and unfelt.)

Assume EVERYONE can be a carrier.

[Nemo2]

Quote:

Originally Posted by JoeWras Clearly, singing can forcefully expel aerosols.

The Korean vid I posted, (on one of the numerous COVID threads), mentions a particular church/sect/group meeting/singing in a closed environment, (being wintertime), and displaying high contagion numbers.

[gwraigty]

Case Study Shows Asymptomatic Transmission of COVID-19 in China

Quote:

A case study of a family in Zhejiang province, China, shows how coronavirus disease 2019 (COVID-19) can spread before symptoms of the disease emerge, and symptoms can vary widely even in a close family cluster. The study, published in Clinical Infectious Diseases, details how SARS-CoV-2 spread from a presymptomatic carrier to infect 8 of 9 family members from 3 households after a 58-year-old woman (index 1) and 60-year-old man (index 2) attended a Chinese Spring Festival temple activity on January 19. ... The case study demonstrates that COVID-19 is clinically diverse, transmittable during the incubation period and can result in infected patients experiencing no symptoms. The study found that the viral loads were similar between symptomatic and asymptomatic patients.

[JoeWras]

This COVID beast is one sneaky bastard.

Thanks for the article pointer, gwraighty. Another snippet:

Quote:

“These ‘silent patients’ may remain undiagnosed and be able to spread the disease to large number of people,” the study noted. “In summary, there are variations across individuals in the clinical manifestations of COVID19. From our reports, we should pay attention to how to prevent people from being infected by asymptomatic patients and patients who were in their incubation period.”