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Winston

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I can't find "reasons tested" data for the US with a quick search. This is the UK:

Reasons for getting a COVID-19 test: survey of regional and local testing sites between 1 and 4 September - 1 October 2020


In Table 1, 65% were tested because of COVID-19 symptoms or exposure to someone who was symptomatic and, as a result, the resulting "percent positive" figure is not representative of the percent of the general population which is infected. It's probably too high.

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Now add this:

Fauci, FDA, WHO All Now Admit False Results From PCR Tests
January 5, 2021


We have detailed the controversy surrounding America’s COVID “casedemic” and the misleading results of the PCR test and its amplification procedure in great detail over the past few months.

As a reminder, “cycle thresholds” (Ct) are the level at which widely used polymerase chain reaction (PCR) test can detect a sample of the COVID-19 virus.

The higher the number of cycles, the lower the amount of viral load in the sample; the lower the cycles, the more prevalent the virus was in the original sample.

Numerous epidemiological experts have argued that cycle thresholds are an important metric by which patients, the public, and policymakers can make more informed decisions about how infectious and/or sick an individual with a positive COVID-19 test might be.

However, as JustTheNews reports, health departments across the country are failing to collect that data.

Here are a few headlines from those experts and scientific studies:

1. Experts compiled three datasets with officials from the states of Massachusetts, New York and Nevada that conclude:“Up to 90% of the people who tested positive did not carry a virus.”

2. The Wadworth Center, a New York State laboratory, analyzed the results of its July tests at the request of the NYT: 794 positive tests with a Ct of 40: “With a Ct threshold of 35, approximately half of these PCR tests would no longer be considered positive,” said the NYT. “And about 70% would no longer be considered positive with a Ct of 30! “

3. An appeals court in Portugal has ruled that the PCR process is not a reliable test for Sars-Cov-2, and therefore any enforced quarantine based on those test results is unlawful.

4. A new study from the Infectious Diseases Society of America, found that at 25 cycles of amplification, 70% of PCR test “positives” are not “cases” since the virus cannot be cultured, it’s dead. And by 35: 97% of the positives are non-clinical.

5. PCR is not testing for disease, it’s testing for a specific RNA pattern and this is the key pivot. When you crank it up to 25, 70% of the positive results are not really “positives” in any clinical sense, since it cannot make you or anyone else sick.


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Then add this:

2% of people carry 90% of COVID-19 virus, and roommates are safer than you think
16 March 2021


A few "super carriers" with off-the-charts viral loads are likely responsible for the bulk of COVID-19 transmissions, while about half of infected people aren't contagious at all at the time of diagnosis, suggests a new CU Boulder analysis of more than 72,000 test samples.

For the studies—among the largest to date to examine trends in asymptomatic people—researchers analyzed saliva samples collected from students, and some faculty and staff, on the CU Boulder campus between Aug. 17 and Nov. 25.

Asymptomatic students in residence halls are required to test weekly, using a free, highly sensitive saliva-based screening test called RTqPCR (reverse transcription polymerase chain reaction), which detects and quantifies genetic material from the virus that causes COVID-19.

In the fall, out of 72,500 samples taken from asymptomatic people, 1,405 cases of COVID-19 were identified.

"What is so special about these samples is that they are all from infected people with no symptoms—a snapshot of all these seemingly healthy people you assume it is safe to be around," said Sawyer.

Super-carriers = super-spread

Sawyer and her team quantified just how many viral particles, or virions, each of those samples contained, plotted it and compared it to samples from hospitalized patients. A few surprising patterns emerged. First, the distribution of viral loads in the asymptomatic sample was indistinguishable from that of highly symptomatic patients.

"This means that symptoms tell you very little about what is going on inside a person's body," said Sawyer. "Some of these asymptomatic people are carrying a viral load as high as someone who is intubated with COVID in a hospital bed."

Just 2% of all the COVID-positive individuals at CU Boulder carried 90% of the circulating virus. One student with the highest load carried 5%.

Meanwhile, about half of those who tested positive had viral loads so low (below 106 virions per milliliter) that they were probably not carrying live virus anymore—instead they may have just been shedding viral fragments from tissue under repair. Thus, they were probably not contagious.

A second, related study lends further credence to the idea that viral load, or the amount of virus particles a person carries, drives contagion. It found that only one in five university students who tested positive while living in a residence hall infected their roommate. And their viral load was nearly seven times higher than those who didn't spread the virus.

"The takeaway from these studies is that most people with COVID don't get other people sick, but a few people get a lot of people sick," said Sara Sawyer, a professor of molecular, cellular and developmental biology and senior author of the first study. "If you don't have a viral super-carrier sitting near you at dinner, you might be OK. But if you do, you're out of luck. It's a game of roulette so you have to continue to be careful."


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As of today, the 7-Day Average Positivity in the US is 5.5%:


Now, let's do some basic math totally ignoring the likelihood that the percent positive figure is not representative of the general population (too high) due to a skew caused by those choosing to be tested for symptomatic reasons (65%) and a too-high Ct being used in PCR tests resulting in a likely to be very high percentage of people testing positive who are not contagious, that assumption being backed up by the University of Colorado study.

Using a city of 500,000 in the example.

5.5% (positivity) of 500,000 = 0.055 * 500,000 = 27,500 infected

2% (effective spreaders) = 0.02 * 27,500 = 550

So, 550 in a city of 500,000 would be effective spreaders at any given time.

500,000/550 = 1 person in 909.
 

Winston

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Can you summarize that for me? I don't have the attention span
😁 See the last paragraph and the calculations below it. Also, this:

"The takeaway from these studies is that most people with COVID don't get other people sick, but a few people get a lot of people sick," said Sara Sawyer, a professor of molecular, cellular and developmental biology and senior author of the first study. "If you don't have a viral super-carrier sitting near you at dinner, you might be OK. But if you do, you're out of luck. It's a game of roulette so you have to continue to be careful."
 

BABAR

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😁 See the last paragraph and the calculations below it. Also, this:

"The takeaway from these studies is that most people with COVID don't get other people sick, but a few people get a lot of people sick," said Sara Sawyer, a professor of molecular, cellular and developmental biology and senior author of the first study. "If you don't have a viral super-carrier sitting near you at dinner, you might be OK. But if you do, you're out of luck. It's a game of roulette so you have to continue to be careful."
Quite possibly true, but until we get a test that distinguishes which 2% are the superspreaders, I am not sure there are any alternatives to what we already are (or should be) doing, which is vaccinating as fast as we can, wearing masks, and continuing social distancing. As more people get vaccinated, I think we can reduce the social distancing among vaccinated populations enough to keep businesses running, otherwise I think we continue masking and social distancing until this is under control worldwide.

an analogy is early breast cancer, aka Ductal Carcinoma In Situ or DCIS. Traditionally we have always treated this as just “cancer” with lumpectomy or mastectomy. Data now shows that about 50% of those woul never progress to invasive cancer, but the other 50% could and furthermore go on to be fatal if untreated. Currently we have no way to distinguish which is which.

so you could correctly argue that 50% of these patients received no benefit from treatment. But assuming the patient is in otherwise decent health and likely to live say 5 years or more, we treat all of them the same, again because we don’t have any way currently of teasing out which 50% are which.
 

Marc_G

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Just remember, the people with PCR positive results with relatively high cycle counts either HAD the virus sometime recently, and need to be counted as cases, or are in the process of developing an infection, and need to be counted. Or they have a very active current infection and were poorly swabbed during sampling. There's no way to tell the difference just from the test which of these in it is.

It's easy to take some of the references above out of context and come up with a story that this is all overblown. However I support the summary that caution is still needed.
 

Winston

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The intent of this post was simply to reduce paranoia. Effective asymptomatic spreaders are apparently very rare as illustrated by the large, University of Colorado study which confirms these:

Asymptomatic Spread Revisited
November 22, 2020


On June 7 (2020), Dr. Maria Van Kerkhove, head of the WHO’s emerging diseases and zoonosis unit, told a press conference that from the known research, asymptomatic spread was “very rare.” “From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual.” She added for emphasis: “It’s very rare.”

Although I don't trust China data for multiple reasons beyond just mistrust of data due to political influences there, it is also due to something I am investigating and will cover in a future post (hint: genetics and previous exposure to similar viruses resistance in Asians), see this:

Published: 20 November 2020
Post-lockdown SARS-CoV-2 nucleic acid screening in nearly ten million residents of Wuhan, China


Abstract

Stringent COVID-19 control measures were imposed in Wuhan between January 23 and April 8, 2020. Estimates of the prevalence of infection following the release of restrictions could inform post-lockdown pandemic management. Here, we describe a city-wide SARS-CoV-2 nucleic acid screening programme between May 14 and June 1, 2020 in Wuhan. All city residents aged six years or older were eligible and 9,899,828 (92.9%) participated. No new symptomatic cases and 300 asymptomatic cases (detection rate 0.303/10,000, 95% CI 0.270–0.339/10,000) were identified. There were no positive tests amongst 1,174 close contacts of asymptomatic cases. 107 of 34,424 previously recovered COVID-19 patients tested positive again (re-positive rate 0.31%, 95% CI 0.423–0.574%). The prevalence of SARS-CoV-2 infection in Wuhan was therefore very low five to eight weeks after the end of lockdown.
 
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