Credibility of the CDC on SARS-CoV-2

by Elizabeth, jimrandomh5 min read7th Mar 2020117 comments


CoronavirusGovernmentWorld Modeling


One of the main places Americans look for information on coronavirus is the Center for Disease Control and Prevention (abbreviated CDC from the days before “and Prevention” was in the title). That’s natural; “handling contagious epidemics” is not their only job, but it is one of their primary ones, and they position themselves as the authority. At a time when so many things are uncertain, it saves a lot of anxiety (and time, and money) to have an expert source you can turn to and get solid advice.

Unfortunately, the CDC has repeatedly given advice with lots of evidence against it. Below is a list of actions from the CDC that we believe are misleading or otherwise indicative of an underlying problem. If you know of more examples or have information on any of these (for or against), please comment below and we will incorporate into this post.


Dismissed Risk of Infection Via Packages

On the CDC’s coronavirus FAQs pages on 2020-03-04, they say, under “Am I at risk for COVID-19 from a package or products shipping from China?”:

“In general, because of poor survivability of these coronaviruses on surfaces, there is likely very low risk of spread from products or packaging that are shipped over a period of days or weeks at ambient temperatures.”

However, this metareview found that various coronaviruses remained infectious for days at room temperature on certain surfaces (cardboard was not tested, alas) and potentially weeks at lower temperatures. The CDC’s answer is probably correct for packages from China, and it’s possible it’s even right for domestic packages with 2-day shipping, but it is incorrect to say that coronaviruses in general have low survivability, and to the best of my ability to determine, we don’t have the experiments that would prove deliveries are safe.

Blinded Itself to Community Spread

As late as 2020-02-29, the CDC was reporting that there had been no “community spread” of SARS-CoV-2. (Community spread means that the person hadn’t been traveling in an infected area or associating with someone who had). At this time, the CDC would only test a person for SARS-CoV-2 if they had been in China or in close contact with a confirmed COVID-19 case.

Testing Criteria as of 2020-02-11

This not only left them incapable of detecting community spread, it ignored potential cases who had travelled to other countries with known COVID-19 outbreaks.

By 2020-02-13, this had been amended to include

The criteria are intended to serve as guidance for evaluation. Patients should be evaluated and discussed with public health departments on a case-by-case basis. For severely ill individuals, testing can be considered when exposure history is equivocal (e.g., uncertain travel or exposure, or no known exposure) and another etiology has not been identified.

(The CDC describes this change as happening on 2020-02-12, however the Wayback Machine did not capture the page that day).

Based on this announcement on 2020-02-14, when testing that could detect community exposure was happening it was in one of 5 major cities. However as of 2020-03-01 only 472 tests had been done, so no test could have been happening very often.

Between 2020-02-27 and 2020-02-28, the primary guidelines on this page were amended to

However guidance went out on the same day (the 28th) that only listed China as a risk (and even then, only medium risk unless they had been exposed to a confirmed case or travelled to Hubei specifically).

Testing Kits the CDC Sent to Local Labs were Unreliable

They generated too many false positives to be useful.

Hamstrung Detection by Banning 3rd Party Testing (HHS/FDA, not CDC)

One reason the CDC used such stringent criteria for determining who to test was that they had a very limited ability to test, hamstrung further by the faulty tests sent to local labs. Normally private testing would fill the gap, but the department of Health and Human Services invoked emergency measures that created a requirement for special approval of tests, and the FDA didn’t grant it to anyone (source).

There are multiple harrowing stories of people with obvious symptoms and exposure to the virus being turned away from testing, often against a doctor’s pleas:

There is also a rumor that the first case caught in Seattle, which has since turned into the US epicenter of the disease, was caught by a research lab using a loophole to perform unauthorized testing (raising the possibility that it’s worse elsewhere and simply hasn’t been caught).

Ceased to Report Number of Tests Run

Until 2020-03-02, the CDC reported how many tests SARS-CoV-2 tests it had run. On March 2nd, it stopped (before, after). There are many potential reasons for this, none of which inspire confidence. The official reason for this as told to reporter Kelsey Piper is that the number would no longer be representative now that states are running their own tests. So, best case scenario, the CDC can not coordinate enough to count tests performed by other labs.

Gave False Reassurances About Recovered Individuals

As of this writing (2020-03-05), the CDC’s “Share Facts” page states that “Someone who has completed quarantine or has been released from isolation does not pose a risk of infection to other people.”

While it is certainly true that being released from quarantine implies a significantly reduced risk, the quarantine that is typically performed is not stringent enough to say that people released pose no risk. The quarantine procedure performed by the CDC lasts 14 days, after which if symptoms have not appeared, they can be released.

There are case reports of individuals with incubation periods of 27 days and 19 days. There was a case in Texas where a person tested positive after being released from quarantine and visiting a mall.

While an epidemic is still contained, safely quarantining at-risk people means choosing a quarantine period long enough to be confident that, if they haven't shown symptoms, they don't have the disease. When a disease is still contained, this should be risk averse, since a single infected person could start an outbreak. The CDC's 14-day quarantine period was not long enough to catch the cases detailed above.

This was foreseeable. This paper, published Feb 6, estimated the distribution of incubation periods, including the incubation periods of outliers.

The relevant row is the 99th percentile row, which estimates the longest incubation period per 100 people. If you quarantined 100 people, one of them would have an incubation period at least that long. The paper estimates this using three different methods; two of those estimates are greater than 14 days, and all three estimates put significant probability on incubation periods longer than 14 days.

There are also reports of the virus re-emerging in patients who were believed to have recovered.

Conflated Genetics and Environmental Exposure

This is a tough topic to write about.

Cruelty to people because they have or might have a disease is never okay. And the vast majority of people who were cruel to Asian-appearing people in the early days of an epidemic were doing it to healthy people out of knee jerk fear and antagonism, not a measured, well-informed cost-benefit analysis. When the CDC claimed on 2020-02-29 that "People of Asian descent, including Chinese Americans, are not more likely to get COVID-19 than any other American." they were surely trying to dampen attacks on people who had done nothing wrong and were hurting no one.

But the statement is false. Chinese-Americans are more likely to travel to China or associate with people who have, and thus were more likely to catch SARS-CoV-2. This doesn’t mean they are more likely to catch it given exposure, but they were more likely to be exposed.

The CDC admits this in the page specifically on stigma (2020-02-24), saying “People—including those of Asian descent—who have not recently traveled to China or been in contact with a person who is a confirmed or suspected case of COVID-19 are not at greater risk of acquiring and spreading COVID-19 than other Americans.”

However that same anti-stigma page goes on to say “Viruses cannot target people from specific populations, ethnicities, or racial backgrounds.” This is also false. About 10% of Europeans are immune to HIV, an immunity not found people originating from other areas. So we know it is technically possible for a virus to have differential effects based on race.

Does SARS-CoV-2 in particular have race-related effects? There are people claiming Asian men are more susceptible to SARS-CoV-2 than others due to a higher expression of a certain protein (example). Other people dispute this (example). Right now it is very much an open question.

We can see why the CDC prioritized calming racially-motivated violence over fully explaining their confusion over an unanswered question. It might have been the highest-utility thing to do. But it is important to know that “misrepresenting data in order to produce better actions from the public” is a thing the CDC does.

Discouraged Use of Masks

Which brings us to the CDC’s statement on masks:

CDC does not recommend that people who are well wear a facemask to protect themselves from respiratory diseases, including COVID-19.

The Surgeon General (who is not directly part of the CDC) takes a stronger tack:

While we can’t hold the CDC responsible for the Surgeon General, they are being conflated in a lot of news articles saying or implying that masks are useless for healthy people. They’re (probably) not.

Our best guess is that the CDC is trying to conserve masks for health care professionals and others with the highest need, in the face of a looming mask shortage. That could easily be the optimum mask allocation. I can’t prove the lie wasn’t justified for the greater good. But it is another example of the CDC placing “getting the outcome it wants” over “telling people the literal truth.”

What Does This Mean?

These errors we’ve highlighted tend towards errors of omission: saying something is completely safe when it’s not, saying something is unhelpful when it is, saying the current state is less dangerous than it is. You should include that bias when processing new information from the CDC. Notably we’re not saying any of the things they do recommend are bad: to the best of our knowledge, you should be washing your hands and not touching your face. Vaccines are (mostly) great. But I would not take the CDC saying an activity is safe or unnecessary as the last word on the subject.


117 comments, sorted by Highlighting new comments since Today at 1:00 PM
New Comment
Some comments are truncated due to high volume. (⌘F to expand all)Change truncation settings

Addendum: A whistleblower claims that CDC wanted to advise elderly and fragile people to not fly on commercial airlines, but removed this advice at the White House's direction.

Where the CDC and White House are in conflict, I believe the CDC is more credible (and I believe this is consensus); however, this looks like a clear-cut case where the CDC's political situation forced it to be less honest and understate risk.

4jmh9moThat doesn't seem a really strong source for the claim or what exactly was said. Sounds like a fair degree of reading between lines based on an observation (passage removed). The administration refutes the claim. But, how many of this class of people have been infected (or infected others) due to flying? Alternatively, how do those numbers stack up to cruise ship travels? Did the CDC provide advice on that? Also missing, from what I can tell, is the date of these events -- when did CDC want to provide that advise, when did the decision to make the edit occur? They did update their website last Friday.
9Jayson_Virissimo9moI think we should say "the administration denies the claim".
1jmh9moIf we're splitting that hair then one should be questioning if any whistle was being blown or if simple hearsay was reported by AP. However, Fauci certainly seems to be a person that would have direct knowledge so one might take his statement as factual and so a refutation of the reported hearsay.
4habryka9moMaybe related: []

I agree with some of the sentiments in this post, but I think the claim in the second paragraph "Unfortunately, the CDC has repeatedly given advice with lots of evidence against it", is poorly supported. It suggests that the CDC has given advice that is not just incomplete or somewhat off-base, but that is ineffective and should be ignored. I don't think the points that deal with advice meet that standard:

Packages: The CDC quote explicitly refers to packages from China, so this more a matter of missing advice about what to do in other cases than bad advice.

Masks: At the end of the day, "don't buy masks" seems like good advice that ought to be followed. I get the annoyance that the CDC or others might be trying to downplay the fact masks can help healthy individuals, but that doesn't mean the recommendation is wrong.

Genetics and Environment: The general sentiment of "please keep in mind the odds of a Chinese-American having COVID-19 is very similar to anyone else having COVID-19" is pretty good advice. Sure, you can nitpick the language and say the CDC implied "exactly equal" instead of "very similar", but I think it&... (read more)

But right now, there is no source we could give an uninformed person and say “all you need to do is listen to them”.

A lot of your arguments are of the form "they're saying something untrue in an effort to get people to do the right thing". So isn't pointing an uninformed person at the CDC the correct thing to do, since we assume that on reading it they'll end up doing the right thing?

Separate from the infohazardness of this post (discussed in other comments and fairly specific to the audience), it seems weird to prefer truth over consequences in what we tell arbitrary uninformed people who have no interest in rationality and just want to know what the best thing to do is?

The CDC offers a pretty short list of things to do as far as prevention goes. Surely that can't be all there is. Why not post something similar to our Justified Practical Advice thread? At least with low cost/risk ideas like copper tape and taking vitamin D.

And for more unclear or controversial things like wearing a mask, why not offer a nuanced discussion of the trade-offs involved?

The fact that they haven't done these things reduces their credibility in my eyes.

1Davidmanheim9moThe CDC's role is to protect the public as a whole, and communicate with them in ways that minimize the burden of diseases. That doesn't mean you shouldn't trust the CDC, just that you shouldn't assume their goal is to advance epistemic purity. But as far as I can tell, treating them as you sole source and doing exactly what they say, and encouraging others to do the same, would make us all better off than most of the personal advice lesswrong is advising. If the CDC says "disposable masks reduce your chance of becoming infected very slightly," (which is likely true if you use them properly, which, to be clear, most people won't do,) what happens next? The entirely predictable result is that hospitals will not be able to buy them, hospital staff gets sick more often, and then there are staff shortages when they are needed most, leading to far more deaths. That almost certainly makes people as a whole worse off, so they don't do that. (People who wanted to be virtuous instead of selfish might even decide to only do what the CDC recommends.) The CDC also need to communicate in ways that idiots won't misconstrue, and a nuanced discussion of interventions that are unscalable or that could be dangerous if done wrong, or that are difficult to do, would be similarly a really stupid thing for the CDC to publish. Maybe a few examples would help. Is buying an oxygen concentrator a good idea [] ? Possibly, for some people who are able to understand the risks and benefits, and who can monitor their own blood oxygen level while sick enough to need to use. That's absolutely not something the CDC should advise people with a 8th grade reading level to try to do at home. After oxygen concentrators run out in stores because people on Lesswrong decide to do this, (and the people who are most likely to need them cannot get them because the supply is gone and co

"disposable masks reduce your chance of becoming infected very slightly," (which is likely true if you use them properly, which, to be clear, most people won't do)

I am confused why you would say this, after this thread, which suggested a 60%-80% reduced infection rate for influenza-like viruses, and you said you updated on the value of masks when worn by the general population without being fitted. "Very slightly, if you wear them properly" does not seem at all compatible with the evidence, and also seems clearly contradicted by the emphasis that the chinese governments puts on the use of masks. I again would ask for a source for this claim that masks that aren't worn properly only have very little effectiveness. 

9adamzerner9moI think that we should distinguish between two different questions. 1) Is what they're communicating good information for me? 2) Is what they're communicating good for society? I interpreted "credibility" as related to the first question. And my point was that a) the lack of info and b) the lack of nuanced discussion of info makes me think that this credibility is reduced.
2Davidmanheim9moYou're saying that the post is interested in supporting defecting and causing societal harm for personal benefit? I hope that isn't the case, but if it is, we should be far clearer in condemning the provision of information to support people doing this. Am I misunderstanding something?
5adamzerner9moI'm simply commenting on the "personal benefit" part without acknowledging the "good for society" part. Not that the "good for society" part isn't important. Of course it is. But that doesn't mean we shouldn't have conversations about the "personal benefit" part in isolation.
2Davidmanheim9moDefecting in a prisoners dilemma is personally beneficial in isolation - so why look at the whole game, when you can discuss part of it?

Our best guess is that the CDC is trying to conserve masks for health care professionals and others with the highest need, in the face of a looming mask shortage. That could easily be the optimum mask allocation. I can’t prove the lie wasn’t justified for the greater good. But it is another example of the CDC placing “getting the outcome it wants” over “telling people the literal truth.”

As far as I can tell, the CDC hasn't uttered a literal lie about this. In the link, they only say "CDC does not recommend that people who are well wear a facemask to protect themselves from respiratory diseases, including COVID-19", which is a recommendation, rather than a statement of efficacy. It could be motivated by a desire to stop mask-hoarding, as you say, or by the belief that typical usage of masks (including reuse, frequently readjusting the mask and thereby touching your face, etc) actually harms people more than it helps them.

(It's interesting that the link also says "The use of facemasks is also crucial for health workers and people who are taking care of someone in close settings (at home or in a health care facility)." This is (i) an admission that masks can protect you when you're

... (read more)
As far as I can tell, the CDC hasn't uttered a literal lie about this

They definitely haven't written down a literal lie. A lot of news articles say or imply one though, and people are walking away with the impression the CDC has anti-recommended masks. A friend has suggested they're more actively discouraging masks in press conferences, but I couldn't find proof so I left that out.

It's certainly possible that uninformed usage of masks is net-negative, and that it's not possible to inform the general public of correct usage. I haven't seen any evidence of that though. Meanwhile, China is requiring them.

0Davidmanheim9moTo be clear, China started requiring mask usage, but also put in place price controls on masks, and limited mask purchases to 2 per week. Then they ensured that companies were building factories almost overnight to mass produce them [] . These might be good ideas, but as with many other things, it's not within CDC's abilities to do, so I think it's reasonable for the CDC to do what it can to actually reduce risks. And "don't trust CDC because they haven't lied but they didn't advise things that might help but would be harmful overall to the public" is one hell of a take.

The word "cuarenta", in Spanish, means 40.

In English, if the word "quarantine" is applied to an infection-avoiding isolation period of either more or less than 40 days, that's arguably an abuse of linguistic tradition that reveals whoever says it to be in need of remedial education.

Maybe? *I* probably need remedial education, too! Very prestigious linguists have asserted here or there that linguistics is a descriptivist science, and so, from their very prestigious perspective, any use of language is as good as any other use of lan... (read more)

The relevant row is the 99th percentile row, which estimates the longest incubation period per 100 people. If you quarantined 100 people, one of them would have an incubation period at least that long.

This doesn't seem correct to me but not a statistician and not quite sure what we're doing the percentiles.

However, the confidence interval should be a statement about the likelihood the true mean will be found within the range stated (so a 5% chance we got it really wrong). Based on that I don't follow the claim that at least one of the 100 people should have an incubation period at least as long as that (I assume "that" is the mean value estimated).

This section is kind of confusing, and I have tweaked the wording a little bit to try to be clearer. The reason for the confusion is that there are two nested distributions here.

The first is that when a bunch of people get infected, they have different incubation periods; some of them start showing symptoms more quickly than others. This is what the 99th percentile refers to. This makes us uncertain about the incubation period that a particular person will have, but it is not a confidence interval; if we learned how long the incubation periods were for a very large number of people, it wouldn't make the 99th-percentile person's incubation period any closer to the mean incubation period.

The second distribution is our uncertainty about the first distribution; we don't know exactly what fraction of people will have extra-long incubation periods, or how long those periods will be--but we would if we observed enough people. This uncertainty is what the 9.7-17.2, 10.9-20.6, and 12.6-32.2 ranges are referring to.

2jmh9moThanks. After some more looking and thinking I still find both the claim and the answer a bit confusing. Given the, to me, somewhat cryptic comment below which seems to have a some backing, I want to see if I can figure out where I'm missing something everyone sees as so obvious. The days for incubation at the 99% level were estimates of the longest incubation period in days we should expect. Am I still on the same page with everyone on on that? If so then we have the 95% CI range about that mean estimate for the longest expect incubation period. The paper calls CI a credible interval which is a term I've never heard used for statistics. I had taken CI be to the standard confidence interval for the estimated value. From what I can understand the credible interval older (I suppose) confidence interval are similar but not quite the same. The credible interval appears to be narrower in smaller observations than the confidence internal -- but the tend to converge as a limit. If they are really similar concepts then I would think the same interpretation applies as I was using before. That is one cannot say a very strong statement about the estimated value per se using CI ranges. The CI is telling us that the "true" value has a likelihood of falling between the upper and lower range but we don't really know where. So if credible intervals do work as confidence intervals then the claim that out of 100 quarantined people on would have an incubation period at least as long as the estimated days (11.9, 14.1 or 18.5) is not a correct interpretation. What we should be able to say is that we have a credibility level or confidence level of 95% that the longest period we would observer would be between the upper and lower ranges. So where am I really getting off track here?

Well, the two of you have now been seen in the same place at the same time, putting to bed that theory...

There are case reports of individuals with incubation periods of 27 days and 19 days.

The most likely explanation for a 27 day incubation period seems to me that an untraced secondary infection happened. Do we know that people have evidence to rule out such a secondary infection?

6jimrandomh9moThis is certainly possible, and it will never be possible to fully rule out second exposures in cases like this. But note that the 19- and 27-day outliers were not included in the data used by the linked paper that estimated a >14day right tail, and I think it's unlikely for untraced second exposures to have influenced its conclusion.
3ChristianKl9moThere are cases where you can know which exposure is responsible because you did RNA sequencing and can use the mutations to trace the route of infection. Given that we however don't have cheap enough RNA sequencing to widely deploy it, it seems to me unlikely that the 27-day outlier is backed by such considerations.

This NYT Opinion Piece discusses some of the same points as the above, titled Why Telling People They Don’t Need Masks Backfired. It closes:

...during disasters, people can show strikingly altruistic behavior, but interventions by authorities can backfire if they fuel mistrust or treat the public as an adversary rather than people who will step up if treated with respect. Given that even homemade masks may work better than no masks, wearing them might be something to direct people to do while they stay at home more, as we all should.

We will no dou

... (read more)
6Ben Pace8moThe brief post The Bizarre Adventures of the Surgical Mask [] by renaissance man-of-lists Piero Scaruffi makes a lot of similar arguments to the NYT article. Some quotes: He’s very independent and doesn’t try to compete in the attention landscape like most blogs, so I take it as a fairly strong datapoint that these are fairly obvious inconsistencies to the public.
5Ben Pace8moThe highly detailed slideshow on Covid-19 by Michael Lin (PhD-MD) [] has comments reminiscent of the OP. Lin says: He also feels that the CDC is giving lousy information. In their FAQ, their answer to whether your child is at risk for Covid-19 fails to mention that children reliably have much milder disease courses than adults. He says: I think this is consistent with the primary goal of communication from major institutions being to prevent people from doing stupid things, over and above being open and honest.
  • Why talk about SARS-CoV-2 rather than COVID-19?
  • Dot points at end of masks section seem misplaced.
  • This should probably be in block quotes in the post:

The criteria are intended to serve as guidance for evaluation. Patients should be evaluated and discussed with public health departments on a case-by-case basis. For severely ill individuals, testing can be considered when exposure history is equivocal (e.g., uncertain travel or exposure, or no known exposure) and another etiology has not been identified.

5Elizabeth9moSARS-CoV-2 is the virus that causes the disease COVID-19. Most of these statements are about the underlying virus, not the disease. Thanks for pointing out formatting errors, will fix.
6DanielFilan9moShould be SARS-CoV-2. Also thanks so much for writing this!
4Elizabeth9moFixed, thanks.

Is this also wrong?

It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes, but this is not thought to be the main way the virus spreads.

It's certainly contrary to most sources I've seen. Instead CDC claim it spreads "between people who are in close contact with one another (within about 6 feet)" (i. e. through droplets in the air).

8Spiracular9moI am under the impression that the 6ft number came out of the assumption that it only transmits using large droplets, which can move 6ft upon coughing or sneezing. I think it's too early to rule out aerosol transmission (small droplets that cover larger distances, ex: Influenza transmission). This article from CIDRAP [] does a pretty good job of explaining things around this, and mentions that MERS-CoV does have evidence of aerosol transmission, making it quite plausible. This preprint [] mentioned that SARS-CoV-2 (which they called HCoV-19) survived for 3 hours as an aerosol and remained viable. So the quoted claim may turn out to be inaccurate on this level as well, if perhaps somewhat understandable (given their political constraints and the data they had available).
5gwillen9moNote that "survived as an [artificially-generated] aerosol" does not mean that aerosols are generated in substantial numbers in realistic scenarios, nor does it say anything about how infectious the aerosol route is. (Also note that the "3 hour" figure in the preprint's original abstract was grossly misleading; the preprint has been updated to remove it. The real figure implied by their data is longer.)
5Spiracular8moAppreciate the added information. For what it's worth, even if aerosol transmission were proven (which it has not been), I'd still assume that breathing in close contact is higher-risk. SARS-1 and SARS-2 both seem to spread mostly via close contact and large-droplets.

It's uncanny how sometimes we all arrive at the same conclusions privately

[This comment is no longer endorsed by its author]Reply