For the last few minutes I’ve been having fun looking at the COVID-19 test positivity rates for various states at the site of the Coronavirus Resource Center at Johns Hopkins School of Medicine. I’m filled with questions.
For example, although Illinois’s statewide test positivity rate has risen since the middle of June it hasn’t risen a lot and it remains quite low. Gov. Pritzker says he is making his decisions based on science. What science is he basing his decisions on? I’m guessing political science but I’d like to know.
Or take a look at the test positivity rates for New York, New Jersey, and Connecticut. If that isn’t “herd immunity” I would very much like to see what “herd immunity” would look like.
Can someone explain Washington State to me? That looks like an artifact—as though the state were only reporting the numbers of positive tests.
Oregon is a mess and I assume it will get worse. Its test positivity rate is graphic evidence that you can, in fact, contract COVID-19 while “demonstrating”.
Hawaii looks to me like exactly what you’d expect after relaxing a successful containment strategy.
Check out your own states and see what that tells you.
I can comment on Washington state. From the website
https://www.doh.wa.gov/Emergencies/Coronavirus
“August 25: DOH changed the methodology for reporting out testing results. Effective today, total number of tests will be reported on the data dashboard instead of the total individuals who were tested. New positive and negative test counts include all molecular tests by specimen collection date among individuals who have not previously tested positive. Multiple test results from the same day are counted only once and repeat tests on an individual are excluded after the first positive result. This methodology has been applied to the entire 2020 time frame covered in the dashboard. The testing trends remain largely the same. ”
Washington state also stopped reporting “negative” cases for a week while the DOH were regenerating the historical data based on the new reporting method — which is probably what you see.
Not sur show you are determining that they have herd immunity.
Steve
The State of Illinois stopped updating its county-level data over a week ago. Right now it is reporting data from the week of August 9th to 15th.
I don’t think state level data is capturing things. The St. Louis metropolitan area in Illinois and the Peoria area are having its first spike in cases. It would be easier to track if the state website was updated, but it looks like state figures are influenced by dispersion in small metros in August that didn’t have significant positivitity rates in March/April.
Last week our school superintendent tested positive; this is the first person I personally know in this city to have done so. I don’t know her well — her daughter was a classmate of my daughter and they played on a soccer team together — but she seemed to me like a rigid, rule-follower, who probably did what she was supposed to do, but it wasn’t enough.
@steve, it looks like places that have had 25% of the population infected (NY metro; New Orleans) haven’t had an outbreak since. Simplest explanation is that spread is substantially diminished by pre-existing immunity.
The most likely alternative explanation is that mitigation measures are extremely successful in those places. I find that unlikely. Perhaps some combination of both?
“..it looks like places that have had 25% of the population infected (NY metro; New Orleans) haven’t had an outbreak since. Simplest explanation is that spread is substantially diminished by pre-existing immunity.”
Indeed. Reducing the usual threshold stat. And why Sweden has essentially no issues right now.
Two to three weeks of lockdown to “flatten the curve.” Heh. On day 175 now. If I was a cynic I’d think public health wasn’t the real objective. If I was a cynic.
I think the “real objective” has evolved over time. Maybe back in March it was to keep the health care system from being overwhelmed but at this point I think it has become a sort of self-licking lollipop. The elected officials who have (illegally) maintained emergency powers can’t afford to admit they were wrong. The only real real objective at this point is avoiding criticism.
Colorado is at 3% with the positivity curve roughly the same shape as the US as a whole, but with a positivity rate consistently about 1/2 of the US as a whole.
However, for some reason Colorado is still not able to get sufficient tests and timely results. We’re still in the bottom third for testing per capita.
which could provide a partial explanation for the low test positivity rate. If you do zero testing, you’ll have a zero test positivity rate—it’s actually the only likely way to have a zero positivity rate.
I think the evolved portion is absolutely correct, Dave. But after that, avoiding criticism is, I think, a rather charitable explanation. And at the national level I don’t buy it for a second. Its pure politics: he who is in office gets blamed. Creepy.
‘I would very much like to see what “herd immunity†would look like.’
Herd immunity will be reached simultaneously in every state when Biden is sworn in as President.
True herd immunity at 20% makes little sense. This would be unique among viruses. Pre-existing immunity? Would like to see that really confirmed. Bit of a skeptic. I think it more likely that the measures people are taking to reduce spread, personal measures as well as mandated ones, are working pretty well. Look at the flu season in the southern hemisphere. Largely didn’t happen.
https://www.wsj.com/articles/covid-19-measures-have-all-but-wiped-out-the-flu-in-the-southern-hemisphere-11595440682
Steve
I notice that you have presented no competing explanation (I have provided two). I think we should remember Conan Doyle’s admonition (put in the mouth of Sherlock Holmes): when you have eliminated the impossible, whatever remains, however improbable, must be the truth. I am indifferent as to whether what is being seen in New York and New Jersey is effective herd immunity or “true herd immunity”. Does it actually make a difference.
But again, I ask what would herd immunity look like in terms of the graphs on the page to which I link? I suspect it would look a lot like the test positivity rates in New York and New Jersey.
Test positivity rates are around 5% in Ne. Low and stable.
I am very unsure of the composition of the denominator. Some mixture of doctor referrals and employee work requirements and possibly those who just want to know. I’d be happier if they were a random sample.
We just recorded the 20th death attributed to Covid 19 in a community of 330,000. A woman in her 90’s.
So far, the pandemic has not lived up to it’s billing, I’d have to say. Second wave? Silent symptom-less spread? Herd immunity?
Are we just writing headlines?
In 2019, Ne. had 256 traffic deaths, so far in 2020, 390 Covid 19 deaths.
Low and steady, with a few peaks due to reporting lapses I suppose.
https://www.google.com/search?q=covid+deaths+nebraska&rlz=1C1GCEA_enUS878US878&oq=covid+deaths+ne&aqs=chrome.0.0l2j69i57j0l5.6972j0j15&sourceid=chrome&ie=UTF-8
Re: Herd immunity,
What is known but not widespread knowledge is the antibody tests used to estimate number of infected / immune to COVID is certain to be vast underestimates.
This post from science magazine explains why.
https://blogs.sciencemag.org/pipeline/archives/2020/08/18/encouraging-news-about-coronavirus-immunity
“They also detected potentially cross-reactive T cells in 28% of people who had donated blood before the pandemic even hit, which is consistent with several other reports. 41% of the overall patients who were seronegative in antibody tests were still positive for T-cells (CD4+ and CD8+ alike) against coronavirus proteins (Spike, nucleocapsid, and membrane). They conclude that the T-cell response is indeed non-redundant and apparently an important part of immunity to this virus, and that using seroprevalence (antibody levels) as a marker for exposure in a population will almost certainly underestimate the real situation. That’s good news, since it would mean that more people have already been exposed (and are to some good degree immune) than we would think.â€
Actually, I said that I thought it possible that the distancing, masking, washing hands measures people are taking are working. In addition it has always seemed likely that there was some seasonality so we should be close to the natural nadir.
Just dont see herd immunity as likely unless viral spread is dependent upon the Super spreaders and we have gone through those already. My concern is that if people actually start believing we have herd immunity, and we dont, we end up with the double whammy of flu PLUS Covid.
Steve
Some commentors on this topic don’t use the term “herd immunity” because it has a technical meaning that obscures the point.
If one out of four people have already been infected in a given area, plus some have pre-existing resistance or T-cell response, then the virus has less ability to spread, it effectively is less contagious. In places with recent spikes, Arizona, Texas, Florida and Georgia, the reproduction number (Rt) has fallen below 1, which is lower than when these states had lockdowns.
If you use a word incorrectly frequently it loses meaning. So of course if some significant percentage of the population has immunity then spread is less likely.
Steve
Nice bit on nanobodies.
https://www.ucsf.edu/news/2020/08/418241/aeronabs-promise-powerful-inhalable-protection-against-covid-19
Steve
Good article and an interesting technology but the developers would be crazy to market it without serious longitudinal testing in the absence of a waiver of liability at the very least.