CDC *boggling*

[oldalum]

Santa Clara County public health officers and Gov. Newsom don't buy the new CDC guidelines:


""When I first heard about this change in guidelines I actually didn't believe it because it seems entirely bizarre in that it undercuts our basic tenets in how we control an infectious disease," Dr. Cody said." 
. . . " She added that Santa Clara County's health order actually requires this kind of contact tracing-related testing."
. . .

"I do not agree with the CDC policy full stop," Newsom said. "It is not the policy guideline we will embrace in the state of California."

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[teejers1]

Santa Clara County public health officers and Gov. Newsom don't buy the new CDC guidelines:


""When I first heard about this change in guidelines I actually didn't believe it because it seems entirely bizarre in that it undercuts our basic tenets in how we control an infectious disease," Dr. Cody said." 
. . . " She added that Santa Clara County's health order actually requires this kind of contact tracing-related testing."
. . .

"I do not agree with the CDC policy full stop," Newsom said. "It is not the policy guideline we will embrace in the state of California."

article

I find Dr. Cody difficult to take seriously inasmuch as she has no policy, except for "we can't do anything. . . lest the virus kill us all!!"  
And I'm only half-joking.  Plus, SCC is doing such a bang-up job of contact tracing . . .

[Goose]

The CDC changed the guidelines without citing any data. Newsom and Cody both rejected the change without citing any data. That is disturbing IMHO. SCC, California, and the CDC should be able to supply two numbers:

1. The number of people who were tested due to an initial test given because they were named as a contact and were also asymptomatic. Call this number X.
   
2. The percentage of X that tested positive. Call this number P.
   

If X is a very small number compared to the number of total tests given in a jurisdiction, the argument is moot. You might as well test because it isn't a resource driver. One would expect this is not the case, but it must be considered. Next, if P is greater than the nominal percent positive test results in a jurisdiction, you should continue to use the old guidelines. The "expected value" of the test is greater than the average test you are doing, so you want to continue doing them. If P is less than the percentage of COVID-19 in the general population, you for sure should not test these people because they are LESS likely to test positive than a random person. One would expect this won't be the case, but it must be considered. If the results are "in between", the decision becomes more difficult.

One might expect that since the contact is known to have been exposed to COVID-19 that it would be much more probable that a test would produce a positive result than the nominal percent positive in a jurisdiction, but there are good reasons that may not happen. The people going for COVID-19 tests on their own accord are often symptomatic and therefore more probable to test positive. The asymptomatic person who is a contact may not actually have COVID-19. He also may be in the incubation period and will not have enough viral load yet to test positive. The exact profile of how quickly one test positive after initial exposure is not well known yet, and depends on many things that may be specific to a given case and "local" to a given jurisdiction. However, all jurisdictions should know P. If they don't, we are all just guessing.

If P is "in between" (which is likely IMHO), second order effects come into play. The benefit of an "early" test is that if it comes up positive, the contact knows he must isolate instead of quarantine. This might prevent/reduce spread within the family group. However, if the contact is already testing positive, it may be too late. While it would reduce the total number of cases, this "branch" of the infection is terminated in any case.

The second benefit is that contact tracking can start immediately based on the positive test. If any are positive it yields even more contacts. It may be that the contact will remain asymptomatic during his entire infection. In that case, the early test would be the only way that person would ever have been identified as positive and asymptomatic spread has been reduced. However, one must realize the person would be in quarantine anyway, so the reduction generally would be minimal.

The trade-off in deciding to not test all contacts would be if so doing would decrease the time it takes to get test results back to those being tested. If it doesn't do that, there is little reason not to test. I am sure there are estimates of this effect that can be cited to justify (or not) a policy of not automatically testing all contacts. If that is the justification, I would like to see it made public. If P is "almost" big enough, and the projected speed improvement is "small", it isn't worth not testing. If we all knew these numbers we could at least have an informed opinion.

It also must be factored in that none of this really matters if the contact isn't going to quarantine/isolate anyway. In SCC, 32% of the positive tests are "contacts to a case", which I believe is defined as contacts that are in quarantine and test positive, either initially or later. MT can correct me if that isn't right. 32% isn't insignificant, but it also isn't great. In South Korea, the corresponding number is 95%. Second, of that 32%, what is P? If it is "small" (say 5%), not much was accomplished by the initial testing. Based on what San Mateo County is reporting, a large percentage of positive tests, let alone contacts, are not quarantining/isolating. If so, all this is much ado about little.

[OutsiderFan]

Goose, I know you are a really smart person, but, it's really time to stop bending over backwards to find the evidence-based position in the current Executive Branch. Like Maya Angelou famously said: When someone shows you who they are, believe them.  It's been well established that the White House has no regard for truth. It's been well established that the White House will hide information and lie in service of its own agenda. It's been established that it doesn't think it needs to serve all states and all Americans. It has shown it will corrupt every office and apparatus of government and break laws in service of its self-serving agenda.

Now, having said all that, on the topic of asymptomatic testing that you spent a fair amount of energy trying to find a justification for not doing:

And I'll close with this. My sister works in a medical office. She shows no symptoms, but a co-worker showed up sick to work this week and yesterday tested positive. My sister shares a house with her husband and two daughters. She got tested today. Now she has to wait 3 days to get results. There are so many ways I can make a case about the inadequacy of testing and specifically for asymptomatic infected testing, but I won't. I just have to brace for the possibility my sister and her whole family are gonna get Covid-19. And I KNOW inadequate testing will be a primary reason it happened if it does.

[BostonCard]

And I'll close with this. My sister works in a medical office. She shows no symptoms, but a co-worker showed up sick to work this week and yesterday tested positive. My sister shares a house with her husband and two daughters. She got tested today. Now she has to wait 3 days to get results. There are so many ways I can make a case about the inadequacy of testing and specifically for asymptomatic infected testing, but I won't. I just have to brace for the possibility my sister and her whole family are gonna get Covid-19. And I KNOW inadequate testing will be a primary reason it happened if it does.

There are soooo many screw-ups here that have nothing to do with testing.  What the hell is someone who works in a medical office doing showing up sick in the age of COVID-19.  Like, whoever runs that office should have made it crystal clear that no one is to come in sick, and should have sent your sister's sick co-worker home immediately.  That still wouldn't have protected from asymptomatic transmission, but what the hell is the point of doing asymptomatic testing if people are going to go to work with symptoms!  Obviously, this is a good time to plug mandatory sick leave; in the long run, most companies actually have less absenteeism because of the reduction of work-related transmissions.

Secondly, upon exposure to a known COVID-19 case, your sister should have isolated herself from everyone else in the household, regardless of testing.  This would have protected the rest of her household.  Remember, testing gives you a snapshot in time; it's really useful to encourage isolation if positive, but just because it is negative today doesn't mean it won't turn positive tomorrow or the next day, so barring serial quick tests, it is no substitute for isolation.

Lack of testing would not be the primary reason your sister's family would all get COVID-19.  Number one was a co-worker who went to work despite COVID-19 symptoms, and number 2 would be failure to isolate.  Real time information is helpful (and certainly is useful for driving policy and tracing cases), but is no substitute for basic public health measures 

BC

[M T]

From all we know from the post, "showed up sick" might mean felt poorly and had a headache develop at work.  Some of the symptoms of COVID-19 are commonplace.   The coworker showed up sick "this week".  "tested today" = Thursday.  

One timeline is coworker goes to work on Monday and develops a headache.  Goes home that day and feels sicker.  Goes to get a COVID test on Tuesday instead of work. (I presume all test centers emphasize "If you have reason to believe you are sick, quarantine until you get the results back.  If you were a close contact, quarantine for 2 weeks.")  The test results come back on Wed. and are shared with coworkers either Wed. or Thursday.  Sister isolates, does not go into work, and gets test on Thursday.  Results expected Monday . . . . maybe.

The good news is that while the sister may have been exposed on Monday, she probably wasn't infectious until at least Wed. afternoon.  If she started self-quarantining then, she may not have infected anyone.  

The bad news is that a negative on her test on Thursday won't tell her that she's not going to get COVID-19.  If negative, she has to take the test until a positive result, or until 2 weeks post-exposure.  She should quarantine and not go into work during that time.

The impact of a case on a small business can be immediate.  Likely that medical office is closed the rest of this week and maybe all of next week if all the workers are self-quarantining for 14 days.

------
My relative who was exposed and placed under quarantine orders by the county within a day of exposure, was finally tested by the county on day 11 after her exposure.  While she seemingly has no symptoms, if she tests positive, she'll have to isolate until day 21 after her exposure. (Hint: the county isn't paying for her quarantine at a motel.  She's the one the county handed a sleeping bag to and told her to go camp out for 2 weeks in 100-degree weather.)

Consider this for that county:  The county dashboard had this on Tuesday: 

Public Health staff was busy over the weekend however, with three new cases reported on Saturday and two new cases on Sunday.  Three of the cases identified over the weekend are in isolation AND TWO ARE RECOVERED

(my caps)

-------
On Tuesday, I had to run errands.  As I passed El Camino Hospital and the rehab center across the street at 3:34PM, there were 5 people in scrubs standing on the street corner at the light, all without masks, and no one separated by 6'.

[OutsiderFan]

My sister works at a mental health office. Somehow masks are optional in her office and the one who tested positive sits adjacent to her. My sister wears mask all the time, but this asshole wasn’t wearing one. Of course, even if everyone is wearing mask inside, if in same office for hours, they aren’t going to stop spread.

She told me the lack of direction and proper protocols is outrageous. Tracks to what I’ve hear from other places.

[OutsiderFan]

Hey, dabigv13, check this out. Looks like several states in fact now are going to ignore the CDC:

https://www.reuters.com/article/us-healt...SKBN25N31H

[Goose]

Goose, I know you are a really smart person, but, it's really time to stop bending over backwards to find the evidence-based position in the current Executive Branch.
<snip>
Now, having said all that, on the topic of asymptomatic testing that you spent a fair amount of energy trying to find a justification for not doing

OF, I started off what I wrote saying that essentially everybody opining on this issue was not being data driven. The CDC and their critics are both equally guilty. I presented a method to determine if immediately testing contacts was worthwhile. I spent no energy at all trying to find a justification for not immediately testing all contacts. What I did do is spend energy attempting to define under what conditions doing such testing was advisable. If you (or anybody else) want to point out why my analysis is incorrect I would like to hear it.
You seem to think what I wrote serves an agenda. It may be it does, but since I don't know what "P" is in any jurisdiction, it is unclear how that could be true. It is also possible that something written to serve an agenda can actually be correct. If you think I made an error, it would be good to know what that error is, but why I wrote what I did is irrelevant. It is either valid or it isn't.
By now, in this epidemic, every jurisdiction should know what "P" is in their area under the previous guidelines. Without knowing that, deciding to test or not test is a matter of opinion, nothing more. It may be that waiting a few days and testing reveals many more asymptomatic positives. The trade-off would then be delay vs. yield. In any case, we need to optimize our actions by something other than people "gut feel" IMHO.

[magnus]

Belated information,  the CDC updated their guidelines to stress asymptomatic people should be tested.

Better late than never.

---

Speaking of better late than never,  the CDC now acknowledges aerosol transmission in their guidelines. 

https://www.cnn.com/2020/09/20/health/cd...index.html

[BostonCard]

Speaking of better late than never,  the CDC now acknowledges aerosol transmission in their guidelines. 



https://www.cnn.com/2020/09/20/health/cd...index.html

And now the CDC walks it back.

https://www.nytimes.com/2020/09/21/world...ticleShare

The Centers for Disease Control and Prevention quietly introduced — and then on Monday quietly withdrew — guidance on its website acknowledging that the coronavirus is transmitted mainly through the air.

The rapid reversal is another in a string of confusing missteps from the agency regarding official guidance that it posts on its website. The latest debacle concerns the spread of the virus by aerosols, tiny particles containing the virus that can stay aloft for long periods and travel further than six feet.

Aerosol experts noticed on Sunday that the agency had updated its description of how the virus spreads to say that the pathogen is spread primarily by air.

Something, something, mixed messages...

BC

[Goose]

Belated information,  the CDC updated their guidelines to stress asymptomatic people should be tested.

To clarify, I think you are referring to testing people who are contacts of a known COVID-19 case. I am not sure this is necessarily a great idea. As I pointed out previously, it depends on the "yield". If the results of such testing so far indicate that the probability of such a person being positive isn't significantly greater than in the general population, it is arguably a wasted test. Does anybody know what the positive rate of such tests has been? I haven't been able to find that information anywhere.

[oregontim]

We go deeper and deeper into the chasm. Trump's people take over the CDC. In plain site. Without accountability. Thanks, Mr. All-About-Me and his enablers.

Speaking of better late than never,  the CDC now acknowledges aerosol transmission in their guidelines. 







https://www.cnn.com/2020/09/20/health/cd...index.html

And now the CDC walks it back.



https://www.nytimes.com/2020/09/21/world...ticleShare

The Centers for Disease Control and Prevention quietly introduced — and then on Monday quietly withdrew — guidance on its website acknowledging that the coronavirus is transmitted mainly through the air.



The rapid reversal is another in a string of confusing missteps from the agency regarding official guidance that it posts on its website. The latest debacle concerns the spread of the virus by aerosols, tiny particles containing the virus that can stay aloft for long periods and travel further than six feet.



Aerosol experts noticed on Sunday that the agency had updated its description of how the virus spreads to say that the pathogen is spread primarily by air.

Something, something, mixed messages...



BC

[BostonCard]

AS the first reply notes...

Who would have guessed the Deep State was actually populated by Trump cultists? (Answer: everybody should have.)

BC

[JustAnotherFan]

No health experts will be guided by these new guidelines.  

Everyone with a functioning brain knows more testing leads to reduced virus spread and less testing leads to more virus spread.

CDC guidance matters. Hospitals, schools, workplaces will be using these guidelines.

Hopefully they'll all go further than the CDC guidance.

[M T]

Belated information,  the CDC updated their guidelines to stress asymptomatic people should be tested.

To clarify, I think you are referring to testing people who are contacts of a known COVID-19 case. I am not sure this is necessarily a great idea. As I pointed out previously, it depends on the "yield". If the results of such testing so far indicate that the probability of such a person being positive isn't significantly greater than in the general population, it is arguably a wasted test. Does anybody know what the positive rate of such tests has been? I haven't been able to find that information anywhere.

I think "arguably" is stretching things here....

Using SCC numbers. 
Outbreak Associated  1,062  5.9%
Contact to a Case    6,838  38.3%
Travel   33  0.2%
Unknown/Presumed Community Transmission 9,934  55.6%

Using today's 7-day rolling average of 117, there have been about  117*14 = 1638 cases in the last 2 weeks.

For the sake of argument, let's just say there are on average 10 close contacts per case.  Scale it lower or higher, if you wish.
So, of the 1638 cases, there were about 16,380 close contacts.  Of those, roughly 1638 * 0.383 = 627 were found to have COVID-19.
That's 627/16380 = 3.8%

There are about 1.9M (minus 16,380) in the "Haven't been exposed to any of the cases of the last 2 weeks" group.  Out of them during that period, there have been about 1638 * 0.556 = 910 cases.   That's 910/1.9M or a rate of about 0.05%.

3.8% >> 0.05%

Testing of known contacts seems likely to find more cases than testing of the general populace.   I don't have any numbers of asymptomatic vs symptomatic ratios in known contacts vs general populace, but I'd think if anything, an asymptomatic contact is even more likely to test positive over an asymptomatic non-contact.

[Goose]

Belated information,  the CDC updated their guidelines to stress asymptomatic people should be tested.

To clarify, I think you are referring to testing people who are contacts of a known COVID-19 case. I am not sure this is necessarily a great idea. As I pointed out previously, it depends on the "yield". If the results of such testing so far indicate that the probability of such a person being positive isn't significantly greater than in the general population, it is arguably a wasted test. Does anybody know what the positive rate of such tests has been? I haven't been able to find that information anywhere.

I think "arguably" is stretching things here....

Using SCC numbers. 
Outbreak Associated  1,062  5.9%
Contact to a Case    6,838  38.3%
Travel   33  0.2%
Unknown/Presumed Community Transmission 9,934  55.6%

Using today's 7-day rolling average of 117, there have been about  117*14 = 1638 cases in the last 2 weeks.

For the sake of argument, let's just say there are on average 10 close contacts per case.  Scale it lower or higher, if you wish.
So, of the 1638 cases, there were about 16,380 close contacts.  Of those, roughly 1638 * 0.383 = 627 were found to have COVID-19.
That's 627/16380 = 3.8%

There are about 1.9M (minus 16,380) in the "Haven't been exposed to any of the cases of the last 2 weeks" group.  Out of them during that period, there have been about 1638 * 0.556 = 910 cases.   That's 910/1.9M or a rate of about 0.05%.

3.8% >> 0.05%

Testing of known contacts seems likely to find more cases than testing of the general populace.   I don't have any numbers of asymptomatic vs symptomatic ratios in known contacts vs general populace, but I'd think if anything, an asymptomatic contact is even more likely to test positive over an asymptomatic non-contact.

The problem with the above analysis is timing. The SCC number of positives who were contacts to a case includes all contacts who tested positive at any time. They may have been tested initially and been negative, and then a week/a day later felt ill and got tested. The idea that testing people who are known to have been exposed should result in more positives is reasonable. However, it may be that if you test "immediately", they aren't sick yet. Unless you have THAT number, you don't know how effective immediate testing is. It may be that almost nobody who is asymptomatic tests positive when tested "immediately". Perhaps it is better to wait a few days. I don't know the answer, but unfortunately the "contacts to a case" number doesn't tell us.

[M T]

The problem with the above analysis is timing. The SCC number of positives who were contacts to a case includes all contacts who tested positive at any time. They may have been tested initially and been negative, and then a week/a day later felt ill and got tested. The idea that testing people who are known to have been exposed should result in more positives is reasonable. However, it may be that if you test "immediately", they aren't sick yet. Unless you have THAT number, you don't know how effective immediate testing is. It may be that almost nobody who is asymptomatic tests positive when tested "immediately". Perhaps it is better to wait a few days. I don't know the answer, but unfortunately the "contacts to a case" number doesn't tell us.

No, if I were exposed to COVID on April 1 and tested positive on May 30, then the contact would not have been reported.

If the average time to symptoms is 5 days, and a person is infectious 2 days ahead, I'm pretty sure the PCR-RT tests would pick up such an average person around 3 days after exposure. 

A relative who had an exposure on a specific day (and was quarantined by the next day) was told her county wouldn't test her for 5 days after exposure (remember, in quarantine, you can't go get yourself tested; they have to come to you), and in fact didn't test her for 11 days.  Her 14-day quarantine expired before she knew if she was positive (asymptomatic) or negative.
IMO, she should have been tested at 5 days and at 14 days after exposure (if the first was negative and no symptoms have developed).

More testing (say at 8 & 11 days) can give you a better idea of when the disease starts (if asymptomatic) so you can wait out your 10 days in isolation once you get a positive test.  If you test at 14 days and get a (first) positive, you will need to isolate until 24 days after exposure.  That's a long time when maybe you would have tested positive at day 6.

If she tested negative at 5 days and positive at 14 days, she should be counted as one that got it from a contact.  (Remember, she was in quarantine so she wasn't further exposed.)

[Goose]

The problem with the above analysis is timing. The SCC number of positives who were contacts to a case includes all contacts who tested positive at any time. They may have been tested initially and been negative, and then a week/a day later felt ill and got tested. The idea that testing people who are known to have been exposed should result in more positives is reasonable. However, it may be that if you test "immediately", they aren't sick yet. Unless you have THAT number, you don't know how effective immediate testing is. It may be that almost nobody who is asymptomatic tests positive when tested "immediately". Perhaps it is better to wait a few days. I don't know the answer, but unfortunately the "contacts to a case" number doesn't tell us.

No, if I were exposed to COVID on April 1 and tested positive on May 30, then the contact would not have been reported.

Agreed, because you would be beyond the 14 day (at that time the norm) quarantine period. However, if you tested positive on April 5, you would be counted as a contact, as you state below

If the average time to symptoms is 5 days, and a person is infectious 2 days ahead, I'm pretty sure the PCR-RT tests would pick up such an average person around 3 days after exposure.

That is a reasonable plausibility argument. However, many things with this virus that seemed reasonable didn't happen as planned. SCC and all other jurisdictions should know by now what the PDF of the delay from exposure to testing positive. Knowing this, they should be able to chose a "good" time to test. It may be that if you are asymptomatic, there isn't a "good" time because 1) you may have been lucky and didn't get the disease,  or 2) people that remain asymptomatic may generate less viral load and what they do generate may be delayed. These is one known case where the guy tested positive on day 21.

My point is, and remains, that knowing the PDF of conversion to positive should allow testing at an "optimal" time, where optimal is defined in a stated manner, i.e. what the objective is and what the constraints are. Saying that you must test immediately is just as silly as saying you should only test optionally unless you can say why that is so and back it up with numbers. By now, we should have the numbers, say what they are. In both cases, the CDC changed policy without giving us the data justifying the change.

A relative who had an exposure on a specific day (and was quarantined by the next day) was told her county wouldn't test her for 5 days after exposure (remember, in quarantine, you can't go get yourself tested; they have to come to you), and in fact didn't test her for 11 days.  Her 14-day quarantine expired before she knew if she was positive (asymptomatic) or negative.
IMO, she should have been tested at 5 days and at 14 days after exposure (if the first was negative and no symptoms have developed).

Yes, but that is 2 tests, which may increase the delay for other people's test results. It also may not, but again, SCC and all the other jurisdictions should know the sensitivity of delay vs number of tests. The optimal way to test twice, or four times, is undoubtedly different that the optimal way to test once.

More testing (say at 8 & 11 days) can give you a better idea of when the disease starts (if asymptomatic) so you can wait out your 10 days in isolation once you get a positive test.  If you test at 14 days and get a (first) positive, you will need to isolate until 24 days after exposure.  That's a long time when maybe you would have tested positive at day 6.

If she tested negative at 5 days and positive at 14 days, she should be counted as one that got it from a contact.  (Remember, she was in quarantine so she wasn't further exposed.)

I am assuming the SCC contacts to a case number includes anybody who tested positive within 14 days of their known exposures. Not sure that is true, but I think it is. Also, FWIW you can be further exposed in quarantine but not in isolation. In quarantine, you can be quarantined with other people. If one of them converts to positive, the quarantine starts over. It may be your relative quarantined alone, which would amount to isolation.

[magnus]

And now the CDC says that masks _do_ protect the wearer.  

https://www.cnn.com/2020/11/10/health/ma...index.html

Seems like it's taking us 8+ months to get to where Taiwan and other Asian countries were. (unfortunately, I don't mean cases)

I hope their messaging doesn't change again in a few days.