I think we’re going to see a lot more reports like this:
BOSTON — The Centers for Disease Control and Prevention is now “actively looking into†results from universal COVID-19 testing at Pine Street Inn homeless shelter.
The broad-scale testing took place at the shelter in Boston’s South End a week and a half ago because of a small cluster of cases there.
Of the 397 people tested, 146 people tested positive. Not a single one had any symptoms.
“It was like a double knockout punch. The number of positives was shocking, but the fact that 100 percent of the positives had no symptoms was equally shocking,†said Dr. Jim O’Connell, president of Boston Health Care for the Homeless Program, which provides medical care at the city’s shelters.
particularly over time. The article goes on to discuss the implications of those results for testing in Boston’s homeless shelters but I think there’s a lot more to it than that. The assumptions behind much of present policy include that, for example, it’s possible to avoid exposure to SARS-CoV-2. What if it’s sufficiently widespread that you can’t?
Another possible issue is that whatever test they’re using is giving lots of false positives. As I’ve pointed out before a test that produces lots of false positives and lots of false positives is pretty dubious. I wouldn’t want to use its results as a guide for policy.
The sailors on the USS Roosevelt also show a very high rate of asymptomatic positives, as did a group of pregnant women in NYC.
Those two groups might be explained by a young, healthy cohort. My 85 year old Mom tested positive and remained asymptomatic, as did (I think) 3 other residents in her building. While I’m ecstatic that she didn’t become ill, it is harder to explain.
Offhand, I doubt that’s as compelling an explanation for the homeless shelter. 😉
But the homeless tend not to be obese, right?
One of the nursing homes baby Philly had to evacuate because staff failed to show up to work. They were transferred to our area. All got tested. 37 out of about 80 were positive. Most (in the 20s, could tread the exact number as it was fuzzy) had no symptoms. People dont seek aid if they have no symptoms. By the time you have people symptomatic and getting tested, you already have a significant group in your population. Why we need surveillance testing. Good news is that if we wear masks it greatly cuts risks.
Steve
About a third of the homeless meet the standards for obesity.
I suspect worthless tests for what ever reason.
Might be interested in this via hotair.
https://www.statnews.com/2020/04/16/ct-scans-alternative-to-inaccurate-coronavirus-tests/
The current PCR based tests have a 30% false negative, as suspected months ago. And the reasons don’t look fixable by running multiple tests.
And now more doctors are going for CT scans — like Chinese doctors months ago. The US could have saved a lot of time if the CDC had REALLY paid attention to what Chinese doctors were doing.
As with fever CT scans don’t test for COVID-19. They test for its symptoms. Not just Chinese doctors’ reliance on those but the changing statistics on Chinese doctors’ reliance on those is one of the things that calls China’s reported data into question.
PCR tests in general are a lot more prone to low sensitivity (high false negative rate) than low specificity (high false positive rate.) That’s just the nature of the testing, since you are looking for the presence is the antigen. Not finding it just means you didn’t get enough of it in your sample, which is likely to happen when the antigen is only there in low amount like early in the course of an infection.
But false positives would really indicate a faulty test, or cross contamination. That’s why I find it hard to believe it’s happening at a high enough rate to explain the high number of asymptomatic positives, even when counterintuitive like my mom’s place or the homeless shelters.
But if there really are as many asymptomatic carriers as that would imply, that seems odd too. Are there any other human pathogens that we know of that cause death in some groups but no harm at all to many others?
“By the time you have people symptomatic and getting tested, you already have a significant group in your population.â€
Which is why people don’t comply with mass quarantine, and thevstrategy was doomed from the start.
“Good news is that if we wear masks it greatly cuts risks.â€
I’ve read it’s far more effective than people understand.
“Asymptomatic” spread seems to run up against the studies indicating that the greatest viral shedding is at onset of symptoms. The study out a couple of days ago at Nature found that 44% of viral transmission was 2 to 3 days before the appearance of the first symptoms, with transmission declining steadily over the next 7-8 after onset. The only way I can see to fit asymptomatic into such a model is that the viral load was small at the outset and/or the immune response effectively stopped the virus before symptoms could appear. In either case, it would seem that asymptomatic spread would be reduced, relative to cases where there were symptoms.
Here is another sampling serological survey from Stanford looking for antibodies from infection.
https://www.medrxiv.org/content/10.1101/2020.04.14.20062463v1.full.pdf
Here is the key conclusion.
“We conclude that based on seroprevalence sampling of a large regional population, the prevalence of
SARS-CoV-2 antibodies in Santa Clara County was between 2.49% and 4.16% by early April. While this
prevalence may be far smaller than the theoretical final size of the epidemic, it suggests that the number
of infections is 50-85-fold larger than the number of cases currently detected in Santa Clara County.”
It just doesn’t make sense with the surveys that have been published out of Iceland, Germany, or Austria.
PD- Will confess I didnt actually read the Nature study but someone I trust did and they said it was most infectious the day before symptoms occurred. The working theory is the virus first hangs out and multiplies in the sinuses and airway. When it migrates to the lungs you become symptomatic. Seems like it wouldnt be that hard to study and confirm that.
” which is likely to happen when the antigen is only there in low amount like early in the course of an infection.”
In separate reports that have quantified viral shedding and found that in some patients it is just as high when asymptomatic as when very sick.
Steve
The Nature piece was released as a pre-print awhile ago and was just published, but I read you as saying:
published studies can be disregarded in favor of second-hand anecdotes; and presymptomatic are hard to study in contrast to asymptomatic.
Good luck with claiming public policy should be based upon “science.” I see as entering a domain of broad uncertainty in which people are just asserting their personal preferences by selective attributions.
CO-Nice analysis of the Santa Clara results. Very well written and the kind of analysis we need. Math heavy but his explanations will get you by if you cant follow it. Sort version, results are not that reliable. Hard to study an uncommon event w/o a very reliable test.
Steve
https://medium.com/@balajis/peer-review-of-covid-19-antibody-seroprevalence-in-santa-clara-county-california-1f6382258c25
PD- I went to the study. Here is what it said, confirming what my source said. You just dont have time to read everything and also get work done. At some point you have to trust other people.
we inferred that infectiousness started from 2.3 days (95% CI, 0.8–3.0 days) before symptom onset and peaked at 0.7 days (95% CI, −0.2–2.0 days) before symptom onset (Fig. 1c).
Steve