Popular culture Science Skepticism/critical thinking

Did the WHO just say that asymptomatic people with COVID-19 don’t transmit the coronavirus?

A story claiming that the WHO just said that asymptomatic COVID-19 patients don’t transmit coronavirus. Spoilers: It didn’t. However, the WHO’s message added unnecessary confusion and led COVID-19 deniers to say masks and social distancing are not necessary.

I just want to preface this post by noting how amused I was yesterday at how people who have castigated the World Health Organization for its handling of the COVID-19 pandemic, who say the WHO is too beholden to China, who tell us that we shouldn’t take anything the WHO says seriously about the pandemic suddenly shifted to portraying the WHO as the font of scientific truth on COVID-19. The reason, as you might imagine, is that there was a news story. This time around, it was on CNBC, and it was entitled Asymptomatic spread of coronavirus is ‘very rare,’ WHO says. The reason these particular people learned to love the WHO again, as you might imagine, is because they are COVID-19 deniers, people who have downplayed the severity of the pandemic, who promote conspiracy theories about it, who refuse to wear masks or engage in social distancing, and the like. You’ll see why in this passage:

Coronavirus patients without symptoms aren’t driving the spread of the virus, World Health Organization officials said Monday, casting doubt on concerns by some researchers that the disease could be difficult to contain due to asymptomatic infections.

Some people, particularly young and otherwise healthy individuals, who are infected by the coronavirus never develop symptoms or only develop mild symptoms. Others might not develop symptoms until days after they were actually infected.

Preliminary evidence from the earliest outbreaks indicated that the virus could spread from person-to-person contact, even if the carrier didn’t have symptoms. But WHO officials now say that while asymptomatic spread can occur, it is not the main way it’s being transmitted.

“From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual,” Dr. Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit, said at a news briefing from the United Nations agency’s Geneva headquarters. “It’s very rare.”

Van Kerkove then went on to say that government responses should focus on detecting and isolating people with symptoms and then identifying and tracking their contacts. She then did an amazing thing. After having made such a strong statement, she said that more research and data are needed to ‘truly answer’ the question of whether SARS-CoV-2, the coronavirus that causes COVID-19, can spread widely through asymptomatic carriers. My reaction was: Wait, what? How do you know it’s “very rare” then, particularly given the data we have already?

Here’s how, apparently:

“We have a number of reports from countries who are doing very detailed contact tracing,” she said. “They’re following asymptomatic cases. They’re following contacts. And they’re not finding secondary transmission onward. It’s very rare.”

A lot of those of us who follow the COVID-19 pandemic closely were appalled, mainly for two reasons. First, it’s irresponsible to make a statement as seemingly definitive as this if the data used to make the statement aren’t published, particularly when the WHO admits that the answer hasn’t truly been answered yet. Second, the WHO seemed to be conflating asymptomatic COVID-19 with presymptomatic COVID-19. The difference? Asymptomatic means that the person with COVID-19 is infected but never develops symptom, while presymptomatic means that the infected person doesn’t have symptoms now but goes on to become ill. We’ve known from early on in the pandemic that there is presymptomatic COVID-19 transmission, and it wasn’t until later that it even became clear that a significant percentage of people infected with COVID-19 remain completely asymptomatic or so mildly symptomatic that they don’t suspect that they are infected.

A biologist named Carl Bergstrom noted:

The distinction is incredibly important, but let’s look at the actual text of the WHO’s new statement. Again, Dr. Bergstrom pointed me to the relevant passage in the WHO’s current document:

The text:

Among the available published studies, some have described occurrences of transmission from people who did not have symptoms.(21,25-32) For example, among 63 asymptomatically-infected individuals studied in China, there was evidence that 9 (14%) infected another person.(31) Furthermore, among two studies which carefully investigated secondary transmission from cases to contacts, one found no secondary transmission among 91 contacts of 9 asymptomatic cases,(33) while the other reported that 6.4% of cases were attributable to pre-symptomatic transmission.(32) The available data, to date, on onward infection from cases without symptoms comes from a limited number of studies with small samples that are subject to possible recall bias and for which fomite transmission cannot be ruled out.

This is pretty thin gruel. A study of 63 people? A study of 91` contacts of the 9 asymptomatic patients who infected another person? Oddly enough, reference 33 concludes:

In this study, high transmissibility of COVID-19 before and immediately after symptom onset suggests that finding and isolating symptomatic patients alone may not suffice to contain the epidemic, and more generalized measures may be required, such as social distancing.

Actually, the study did suggest that the time of highest transmissibility around the time of symptom onset, but also noted:

Our analysis revealed a similar clinical attack rate between the contacts who only had presymptomatic exposure and those who had postsymptomatic exposure.

The key question is whether the bulk of the transmission from asymptomatic people comes from people who later go on to develop symptoms or whether those who never develop symptoms can transmit the virus, as this population biologist points out:

Rephrasing the question, are asymptomatic or mild cases less infectious than people currently in the presymptomatic phase of COVID-19 infection. As you might imagine, that’s a really difficult question to study, as it requires very widespread testing and followup. One study cited above out of Italy concluded:

We found no statistically significant difference in the viral load (as measured by genome equivalents inferred from the cycle threshold data) of symptomatic versus a asymptomatic patients (p-values 0.6 and 0.2 for E and RdRp genes, respectively, Exact Wilcoxon-Mann-Whitney test). Contact tracing of the newly infected cases and transmission chain reconstruction revealed that most new infections in the second survey were infected in the community before the lockdown or from asymptomatic infections living in the same household.

We will look at this study more later in this post.

There’s also bias in contact tracing methodology due to delays between infection and testing. First of all, a negative swab test does not rule out infection even if you don’t have symptoms:

She further notes that most people who are tested have had at least mild symptoms for several days and were infected 5-6 days before that, meaning that the person who infected them was infectious 8-11 days ago, and, if that person was asymptomatic there’s a decent (although not precisely known) chance that they would test negative when traced, as the virus can be cleared in two weeks (which is why the usual self-quarantine period recommended for those who are thought to have been exposed to the coronavirus is two weeks). It’s possible that asymptomatic people clear the virus faster than presymptomatic people and are thus more likely to test negative at, say, 10 days. If that’s the case, though, this could happen:

Eric Topol also weighed in. The advantage of citing him is that he recently co-authored a review article on the prevalence of asymptomatic SARS-CoV-2 infection. Noting that it’s been suspected that infected persons who remain asymptomatic play a significant role in the pandemic, he and Daniel Oran tried to quantify the percentage of asymptomatic COVID-19 cases. First, they note:

In the early months of the coronavirus disease 2019 (COVID-19) pandemic, an iconic image has been the “proned” patient in intensive care, gasping for breath, in imminent need of artificial ventilation. This is the deadly face of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which as of 26 May 2020 had claimed more than 348 000 lives worldwide (1). But it is not the only face, because SARS-CoV-2 now seems to have a dual nature: tragically lethal in some persons and surprisingly benign in others.

Since February 2020 (2, 3), there have been reports of persons who were infected with SARS-CoV-2 but did not develop symptoms of COVID-19. In some cases (4, 5), the viral load of such asymptomatic persons has been equal to that of symptomatic persons, suggesting similar potential for viral transmission. The prevalence of asymptomatic SARS-CoV-2 infection, however, has remained uncertain. We sought to review and synthesize the available evidence on testing for SARS-CoV-2 infection, carried out by real-time reverse transcriptase polymerase chain reaction using nasopharyngeal swabs in all studies that specified the method of testing.

To this end, they examined 16 cohorts from all over the world where COVID-19 outbreaks occurred, including, for example, cohorts from Europe, the Princess Cruise Ship, the aircraft carrier USS Theodore Roosevelt and the French aircraft carrier Charles de Gaulle, nursing home residents in Washington, and inmates in Arkansas, North Carolina, Ohio, and Virginia among others. They estimated that asymptomatic infections might account for 40-45% of COVID-19 cases and that these asymptomatic patients can also transmit the virus for up to 14 days:

At the beginning and end of a 14-day lockdown imposed by authorities in the northern Italian town of Vo’ (7), researchers collected nasopharyngeal swabs from 2812 residents during the first sampling effort and 2343 during the second; this represented 85.9% and 71.5%, respectively, of the entire population. In the first group, 30 (41.1%) of 73 persons who tested positive for SARS-CoV-2 had no symptoms. In the second, 13 (44.8%) of 29 who tested positive were asymptomatic. According to the researchers, in the roughly 2-week period between the sampling efforts, none of the asymptomatic persons developed any symptoms of COVID-19. In addition, through contact tracing, they confirmed that several new cases of SARS-CoV-2 infection that appeared during the second sampling had been caused by exposure to asymptomatic persons.

Then, the USS Theodore Roosevelt:

The first case of SARS-CoV-2 infection aboard the American aircraft carrier U.S.S. Theodore Roosevelt was diagnosed on 22 March 2020 (24). As of 24 April, 4954 crew members had been tested for the virus; 856 (17.3%) tested positive (12). According to a news report, about 60% of those with positive results were asymptomatic (25). After an extended period of isolation, many of these asymptomatic persons continued to test positive for SARS-CoV-2. An internal U.S. Navy document stated, “Results of out-testing portions of the [Theodore Roosevelt] crew following 14 days of quarantine leads us to reevaluate our assessment of how the virus can remain active in an asymptomatic host” (26).

The Charles de Gaulle:

On 8 April 2020, crew members aboard the French naval vessel Charles de Gaulle first began showing symptoms of COVID-19, 24 days after last having had contact with those outside the ship while docked on 15 March (27). On 10 April, 50 crew members received positive test results for SARS-CoV-2. The entire crew of 1760 was subsequently tested. As of 18 April, 1046 (59.4%) had tested positive, and of these, nearly 50% were asymptomatic (13).

Overall, the authors conclude that asymptomatic transmission is a major factor in the spread of COVID-19. It’s obviously not perfect. For one thing, some of the cohorts did not have longitudinal data; i.e., the cohorts weren’t followed long enough to tell how may asymptomatic patients developed symptoms. In other words, how many asymptomatic people were actually presymptomatic? It is thus possible that Oran and Topol significantly overestimated the percentage of COVID-19 infections that are asymptomatic, although

Confusing the issue was the observation from the Diamond Princess cruise ship that among 104 passengers who tested positive for coronavirus but never developed symptoms and underwent CT scans of the chest, lung opacities were detected in 54% of these asymptomatic patients, suggesting subclinical changes to the lung in a high proportion of “asymptomatic” patients, as was published in this study. This is what we refer to as subclinical disease.

The bottom line is simple. It’s possible that asymptomatic patients don’t transmit the virus as much as symptomatic or presymptomatic people with COVID-19. However, even if that’s true, all it would mean is that the percentage of infected patients without symptoms who are truly asymptomatic would constitute less of a risk of infection. Those who are presymptomatic would still be infectious while they don’t have any symptoms. Even if asymptomatic COVID-19 patients are much less likely to transmit the virus (a contention that goes against a fair amount of evidence that we already have and about which the kindest thing we can say is that it’s unproven), we already have abundant evidence that presymptomatic people can transmit the virus. Even if asymptomatic COVID-19 patients are much less likely to transmit the virus, conflating them and presymptomatic patients, as the WHO appears to be doing, does not mean that concentrating only on symptomatic persons with contact-tracing will effectively shut down transmission, both because of the time bias in contact tracing and testing but also because presymptomatic people will continue about their normal lives.

What do we need to get a handle on this question? Oran and Topol tell us:

As noted earlier, the data and studies reviewed here are imperfect in many ways. The ideal study of asymptomatic SARS-CoV-2 infection has yet to be done. What might that study look like? Most important, it must include a large, representative sample of the general population, similar to the U.S. serosurvey for which the National Institutes of Health is currently recruiting (31). In contrast to the narrowly defined cohorts here, it will be illuminating to have data that accurately reflect the population at large. In addition, longitudinal data must be collected over a sufficiently long time to distinguish between asymptomatic and presymptomatic cases.

It’s a bit puzzling that a study like this hasn’t yet been done, but it has only been recently that we’ve had enough testing capability to undertake such a large scale study. Absent such a study, it’s really irresponsible of the WHO to make a recommendation like this based on so little data and communicated so poorly.

By Orac

Orac is the nom de blog of a humble surgeon/scientist who has an ego just big enough to delude himself that someone, somewhere might actually give a rodent's posterior about his copious verbal meanderings, but just barely small enough to admit to himself that few probably will. That surgeon is otherwise known as David Gorski.

That this particular surgeon has chosen his nom de blog based on a rather cranky and arrogant computer shaped like a clear box of blinking lights that he originally encountered when he became a fan of a 35 year old British SF television show whose special effects were renowned for their BBC/Doctor Who-style low budget look, but whose stories nonetheless resulted in some of the best, most innovative science fiction ever televised, should tell you nearly all that you need to know about Orac. (That, and the length of the preceding sentence.)

DISCLAIMER:: The various written meanderings here are the opinions of Orac and Orac alone, written on his own time. They should never be construed as representing the opinions of any other person or entity, especially Orac's cancer center, department of surgery, medical school, or university. Also note that Orac is nonpartisan; he is more than willing to criticize the statements of anyone, regardless of of political leanings, if that anyone advocates pseudoscience or quackery. Finally, medical commentary is not to be construed in any way as medical advice.

To contact Orac: [email protected]

79 replies on “Did the WHO just say that asymptomatic people with COVID-19 don’t transmit the coronavirus?”

In the absence of an upvote facility and insufficient background knowledge to otherwise add to the conversation may I just say a heartfelt thank you for your efforts here and in all your posts.

There is, of course, a difference between a military ship where the crew is composed of young, health adults, and a cruise ship carrying mostly older passengers, many of whom probably have underlying medical conditions.

Do we know if any imaging was done on the sailors to see if any of them had subclinical disease as well?

Buffalo protester shoved by Police could be an ANTIFA provocateur. 75 year old Martin Gugino was pushed away after appearing to scan police communications in order to black out the equipment. @OANN I watched, he fell harder than was pushed. Was aiming scanner. Could be a set up?
— Donald J. Trump (@realDonaldTrump) June 9, 2020

My rolled up Orec HEPA bag and sealed facepiece didn’t get any love. ?

WHO has been all kinds of ambiguous of late. It is almost like a cop giving conflicting orders* and the victim is like “Say what, now….” BANG BANG….BANG BANG BANG BANG {reloads} BANG!

CDC might can blame it on Trump but WHO? I suppose they have never been outstandingly competent but I don’t think they are in disarray now simply because Trump twertted out something mean about them. Hmm. I wander what else it could beijing?

*Trained cops are allowed to get nervous and just start a’blastin’ while untrained, unarmed civilians must remain calm with a gun pointed at them.

Asymptomatic, pre-symptomatic… What’s the diff? /sarc
Let’s make a recommendation to discount asymptomatic cases and focus on symptomatic cases when it comes to tracking and contact tracing.
If the asymptomatic case should really have been pre-symptomatic and develops symptoms we can always get into our time machine and go back a couple weeks to monitor this “asymptomatic case” as a pre-symptomaic case.
But, of course, this recommendation may all be BS and more research is needed. /sarc again
This is a lesson on how not to do science communications to the general public.
This is a lesson on how to invite the woo-woos to go off the deep end with their anti-science conspiracy theories.
What the hell is wrong with the WHO?

Does anyone think it’s possible that asymptomatic people don’t actually have Covid-19 at all? My understanding (which I’m sure someone will correct if wrong) of the testing is that it just tests for RNA, and not specifically for Covid-19, so they might be assumed to have Covid-19, but actually have something else (that may be similar)?

COVID-19 is the disease phenotype. I’m fine with saying that asymptomatic, infected people don’t have the disease, but they carry, and can transmit, SARS-CoV-2, the causative virus.

Asymptomatic patients can transmit the virus. I think that is clear. It is also clear is that around half of infections are either asymptomatic or minimally symptomatic. Perhaps some of those who were asymptomatic really had minimal symptoms that they either forgot or overlooked. Hopefully, someone will study that issue.

I don’t trust the WHO here. I think they dropped the ball. When I read that yesterday, I was really puzzled. They are usually pretty good on subjects like this one. Muddling the situation like this has the potential to cause real damage.

RT-PCR with well-designed primers and probes is highly specific for the target RNA. It is very unlikely that anything other than SARS-CoV-2 would yield a positive test result. False positives do sometimes happen due to poor lab technique resulting in contamination of a negative specimen but that is rare unless the lab is sloppy.

The problem with PCR is that it is extremely sensitive. Fragments of non-viable viral DNA can give positive tests. That’s why we are being very cagey about what a positive test means in some settings. My father in law was infected in a nursing home. He was under the weather for a couple of days and has been feeling fine since. He is 89 years old. The protocol is for recovered patients to be transferred back to their regular rooms 28 days after symptom onset. They do not retest them because of this issue. I suspect some of the early reports about patients being reinfected are due to false positive PCRs.

I’d agree that at least some of the reports of reinfection are very likely due to residual non-viable viral bits, but the fact remains that PCR, done properly, is extremely specific. It could indeed detect remnants of SARS-CoV-2 in someone who has recovered or contamination due to bad lab practices, but I’ve seen absolutely nothing to suggest that that any of the tests used anywhere are producing positives on RNA that doesn’t belong to SARS-CoV-2. I don’t know anything about the risk of false positive due to SARS-CoV or MERS-CoV, but the number of people with the former is (believed to be) zero and with the latter is negligible.

Without careful auditing, the fraction of false positives due to poor lab techniques are just completely unknown. (I know that if I were in a position where, in court, a lab claimed my DNA was found at some crime scene, the first question I’d ask is “What is the error rate at your lab?” (with the expectation it would greatly exceed the probability that my DNA would match someone else’s. I see it as a question that they’d likely really not want to answer, either because they knew their error rate was excessive or they weren’t doing adequate work to evaluate the rate.)

The specificity of a lot of the antibody tests, on the other hand, seems to be somewhere between not very good and worse than useless. I checked the FDA site a day or two ago and the number of antibody tests is down to about 200, with only 9 with regular approval.

Michael Finfer, MD: “Fragments of non-viable viral DNA can give positive tests. That’s why we are being very cagey about what a positive test means in some settings.”
And unfortunately testing for the viability/infectivity of a viral particle is both a lot harder and a lot more dangerous to the technician than PCR (not to mention takes a lot longer) so for now I think we’re stuck with the PCR.

I hope your FIL stays safe.

” This is a lesson on how not to do science communications to the general public”

Agreed. I wonder how many people who have heard the report later go back and check to see if it was critiqued or amended.

Over the past months, I’ve tracked areas other than my own because of my SO’s relatives who live in … shall we say?- less enlightened environs which they brag about -which truthfully have been rather cavalier about re-opening or following instructions about social distancing/ masks. and of course, have also seen rebellion in SoCal ( compared to NorCal) and other places..
et Voila!– guess which places are experiencing problem? ( WaPo 14 states show increases) Also, a few states have reported Covid data in dodgy ways ( FL, GA) or have done less testing in general ( AZ) .Especially alarming is the situation now in Arizona where increases threaten hospital / ICU capacity. Utah is rising quickly as well.

The overall Covid figures look good because of huge improvements in NY, NJ, IL,etc**. If you report graphs by region, you can see the difference.
I also worry about the aftermath of the protests- although protests are extremely necessary- I just hope that the social distancing in marches ( yes, it was often visible) , masks worn and outdoor environment helps to keep activists safe I hope they didn’t believe that youth alone would protect them. We’ll see: it’s been two weeks since Mr Floyd’s death.

** it’s not all bad news: measures like shutdowns, masks, social distancing may have prevented a huge number of cases. You’ll see the figures yourself: amazing!.

And just to add to the confusion there’s this:
Fauci touching on this subject in an interview yesterday –
“Q – If you have that measure of protection [antibodies] can you still be a carrier and infect other people?
Fauci – That’s again unknown but I think as long as there’s active virus in you, you can transmit it.
Q – What about the people that are aymptomatic – that are virus positive? There is a lot of concern that they can spread this virus even though they feel fine.
Fauci – There are many good examples of outbreaks in which a very high percentage of the people were completely asymptomatic but they were clearly spreading the virus from one to another. So there’s very little doubt anymore that someone who’s without symptoms cannot spread it… They definitely can.

What is a layman to make of the statements of Fauci and the WHO?

The downfall of focusing on STEM education at the expense of social sciences and humanities. Doesn’t matter how much you know if you can’t communicate it clearly.

It seems ridiculously reckless for the WHO to go off half cocked and release a statement like this at the very moment that lockdowns are ending and summer begins in the northern hemisphere.

Apart from the mixed messaging and the distrust and confusion this causes, which is a very significant long term issue, they have essentially given Covid deniers a blank cheque to do whatever they want and cite the work of the once reviled WHO as justification.

this WHO statement is being shared in hundreds of thousands of family group chats and text chains as justification for beach vacations, Father’s Day gatherings and the like by the resident “skeptic”.

And as always, the retraction never gets the attention of the original headline. Only this time the damage may be thousands of deaths by Labor Day.

Interesting data tidbit: Alberta has tested just under 15 000 asymptomatic people since May 12. Only 6 people tested positive.

I don’t really know what should be made of this. I presume that most of the people were self-selected for testing (testing was opened up to anyone who wanted to be tested) so the randomness of the sample is unknown, at least to me. Maybe it means that the prevalence of asymptomatic people is low. It would certainly be interesting to test all those people for antibodies.

On the topic of antibody tests – anyone know if the Roche test really is as specific as the company claims?

I am having difficulty making sense of some parts of this situation, including why there are variable testing results in some populations, particularly with regard to asymptomatic infections, and why the disease seems to harm a greater proportion of patients in some areas and less than others.

I suspect that it will take years to fully comprehend what’s been going on. In the meantime, we just have to do the best we can.

And wouldn’t you know? Mikey ( Natural News) is using the WHO pronouncement to insist that vaccines won’t be needed!

He and the other idiot downplay the seriousness** of Covid so that they can insult SBM, sell products and of course, discount vaccines.

** the people who died were dying already from serious/ terminal conditions ( PRN)

and the other idiot

You’ll have to narrow it down 🙂
There were plenty full-time professional idiots who saw the pandemic as the perfect occasion to remind the whole world of their idiocies.

(“It was a Tuesday”
“ah, now I see, it’s Gary”)

@ Athaic:

Although you may imagine that I present material from purely for comic relief whilst we read about raging pandemics and frightening health concerns, I can assure you that my own aims include getting SB people to understand the depths of mis-information and mal-education broadcast by that outlet that endangers listeners’ mental and physical health and economic/ social well being. It is a cornucopia of trashy advice, bad counselling and ludicrous educational/ investment guidance that does no one any good.

Some highlights:
eating meat, wheat and dairy are deadly
vaccines are an abomination
hospitals are dangerous
never support major parties in elections ( only third or fourth parties)
never invest in the stock market/ bonds
never live in or near cities
talk your children/ grand children out of going to college ( trade schools instead)
never incur debt for any reason
become an organic farmer or a craftsman
supplements and juices cure everything
disregard doctors
don’t believe most research
electronics cause biological harms
encourage flat taxes
avoid mainstream media
etc etc etc

The grand idiot uses his platform to indoctrinate followers through a steady diet of conjured research data ( misleading, mis-quoted ) and his string of faux credentials and phoney CV. He rages against Wikipedia, SBM and RI because they reveal his MO..
Naive listeners take his swill seriously as he tells them to avoid reality based information and educators.
I know he has a large following and also enables other woo/ ant-vax perpetrators.
He’s been pushed off of Facebook and other social media but has his own system.

@Denice Walter:
Well that’s a horrifying collection of positions sure to decrease his listeners’ lifespans and make them miserable in the process. Although he could shorten it up substantially by saying “avoid any and all ways to increase your income so you’ll be too poor to go to the doctor”.

I don’t even want to mock, it’s just too sad.

I’m glad you’re here to make sense of it all, Orac. We need more science communicators like you–but communicators who do this as their career full-time (versus you somehow doing this in between patients, surgeries and research…I don’t know how you do it!).

Just came across news reports that she walked back the asymptomatic transmission comment and said that it was never a WHO position.


From History, Typhoid Mary, a cook who worked for wealthy families in the early 20th Century, perfectly healthy but carried the typhoid bacteria. From Wikipedia “infected 53 people, three of whom died.”

Asymptomatic simply means that due to various factors, e.g., genetics, that one’s immune system is holding microbe in check, that is, levels too low to cause noticeable bodily changes; but doesn’t mean that live microbes not present and doesn’t mean they can’t be spread. In Typhoid Mary’s case through oral means, food; but for SARS-CoV-2 through mainly airborne (directly from viruses, viruses attached to minuscule droplets) and to a lesser extent some from fomites (inanimate objects, e.g. doorknobs). And there is evidence of asymptomatic spreading. While risk less for younger healthier people, some can also become deathly sick, and others can just pass it on to friends and loved ones, some young with comorbidities, e.g., diabetes and some old with or without comorbidities. Given everything I know about microbes, until solid research disproves this, highly unlikely, I go with the precautionary principle, err on the side of caution.

And they have found asymptomatic superspreaders, that is, for some reason these people harbor higher doses and/or manage to spread more and further.

From History, Typhoid Mary, a cook who worked for wealthy families in the early 20th Century,

Nineteenth century. And she did work for the gentry, until she didn’t.

I hadn’t heard the bit about the gallstones before.

@ Narad

“From 1900 to 1907, Mallon worked as a cook in the New York City area for eight families, seven of which contracted typhoid.”

She probably did work before 20th Century given she was born in 1869; but, for whatever reason (she probably contracted in around the time asymptomically, the first evidence people contracted typhoid from her was exactly as I wrote “early 20th Century.” Once more you are being an asshole for no apparent reason. Why?

CBC is reporting “WHO backtracks on claim that asymptomatic spread of COVID-19 is ‘very rare'”

“And in that [context], I used the phrase ‘very rare.’ I think that that’s misunderstanding [sic] to state that asymptomatic transmission globally is very rare. What I was referring to was a subset of studies… [that say that] when we follow asymptomatic cases, it is very rare—and I used the phrase very rare—that we found a secondary transmission.”

She went on to note that modeling groups have also worked to estimate the proportion of asymptomatic cases and asymptomatic transmission, which result in wide ranges. Some models estimate around 40 percent of transmission may be due to asymptomatic cases, she noted, “but those are from models, and I didn’t include that in my answer yesterday, but I wanted to make sure that I included it here.”

…The WHO has consistently struggled to clearly communicate the issues and data around asymptomatic and pre-symptomatic transmission.

When reporters and members of the public ask about symptomless spread—which we are all rightly concerned about—the conversation typically veers to a pedantic discussion on asymptomatic case definition.

Instead, what the organization should be doing is making clear that symptomless spread is certainly happening. And although we don’t yet know to what extent, pre-symptomatic spread very well may make up a significant portion of transmission. As such, we need to take precautions to prevent that spread.

I expect my trump loving, fox news watching father will be telling me about this tomorrow. I can’t wait. Should be fun. /not

Covid-19 deniers who loathe the WHO except when it seems to support their beliefs, are like antivaxers who revile the CDC but eagerly cite what it says about vaccine ingredients.

If you think these agencies are lying servants of Satan, why are you approvingly quoting them?


I have disliked the WHO immensely for years but I knew their declaration about asymptomatic carriers was wrong. However, it has already been posted on two large antivax pages with over 200,000 members & shared from there over 2,000 times. I am antivax & I won’t be quoting them. I find it ironic as well. Understand that the antivax only quote the WHO as an appeal to authority. For the benefit of you.

Not your biggest worry though, if vaccines are a priority, especially any COVID vaccine; the bigger issue is that many provax people are now saying the WHO has lost all credibility Their new back tracking stance is only adding to that. It is too late. Pity, as the WHO advocates for vaccines & will likely be strongly encouraging mandates for any new COVID vax. Bad timing.

Anyway; good post, Orac.

@ Christine Kincaid

Crawl back under your rock. Despite your immense stupidity, if one actually looks at the history of the WHO it has accomplished quite a bit. However, historically it has actually been undermined by several powerful nations; the U.S. number one. And it has not lost all credibility. In fact, most if not all medical and public health organizations around the world are protesting Trump’s cutting of funds.

Did you actually read Orac’s post carefully? Apparently not because the WHO didn’t. I guess you are so stupid you didn’t even understand the title.

I and others have pointed out just how wrong you have been in your comments; but you ignore and just keep making a fool of yourself.

Yep, the WHO supports vaccinations; but so does history of vaccine-preventable infectious diseases, so does all major medical and public health organizations, so does 10s of thousands of peer-reviewed journal articles and so do an understanding of immunology, microbiology, and epidemiology, subjects you continue to display complete ignorance of.

Another book I know you won’t read:

Marcos Cueto, Theodore M. Brown and Elizabeth Fee (2019). The World Health Organization: A History. Cambridge University Press.

You know better than WHO. You know better than the provaxxers. You know better than the antivaxxers. You’re hyperlexic and read with superior speed and comprehension. Yet you can’t figure out the difference between paarlytic polio and non-polio paralysis, and when called on it, refuse to response, as if that will make it like it never happened. Seriously, how do you manage to fit your ego through the door?

@Christine KIncaid You reallly love infectious diseases. do you not ? Eradicating smallpox is really hateful ? It is not.

Its not as if the WHO is the source of all health advice and research in the world. Vaccination is recommended by ALL national health organisations.

Also, why dislike them? Except for personal reasons to do with their advice countering your own opinions? The principle of the WHO is fantastic. The execution may not be.

Thanks Doug and Michael Finfer for answering my question. As you say, it looks like the WHO is backtracking now so let’s see what happens next. At best it’s very confusing, and I’d really rather not think too much about what’s worse than that!

@ Joel,

I know what they WHO said & what the WHO didn’t say & I read Orac’s post very carefully.

I’m not the hypocritical WHO-hater who is now proclaiming the WHO’s misspoken comment all over the internet; I didn’t like them before & I knew this last mistake by them was downright dangerous. They handed the media the ball & the media ran with it & the headline is now being screamed from the rooftops. The only thing retraction has served to do is to make them seem less credible.

They screwed up. COVID-19 may be novel but it is still a virus & the headlines were WRONG. Are you really excusing this as a result of ‘undermining’ by governments?

@ Christine Kincaid

“I’m not the hypocritical WHO-hater who is now proclaiming the WHO’s misspoken comment all over the internet”.

Thanks. Hate is much more understandable when it’s not hypocritical. Not that Hate is Nirvana, but at least, with the hypocrisy out of the way, we can discuss it. Won’t be with me, though…

“Are you really excusing this as a result of ‘undermining’ by governments?”

I didn’t get this one. If you’d care to explain your line of thought…

@ F68.10,

Well, Orac did a good job at explaining WHAT the WHO did wrong but I still don’t understand WHY they did it. Did they not understand what it would mean? I find that hard to believe; they are usually so careful to preserve the provaccine narrative. So when Joel said:

“Despite your immense stupidity, if one actually looks at the history of the WHO it has accomplished quite a bit. However, historically it has actually been undermined by several powerful nations; the U.S. number one.”

It sounded to me like he was saying that this “undermining” led to their blunder & I just don’t think that is possible.

@ Christine Kincaid

Whether they made a mistake or not, your world of black and white is clear. If they did make a mistake, which I doubt, they corrected it post haste as opposed to you who has NEVER even considered you may be wrong about vaccines, despite not understanding immunology, microbiology, epidemiology, the history and present status of vaccine-preventable diseases.

And the fact that you admit you didn’t like them before says it all. You have NO idea of what they have accomplished. Yep, they are an international organization, limited by member states, so they don’t have the independence and independent resources needed; but, despite this, without them we would be in much worse trouble. They are the only organization that coordinates data, reports, etc. from all over the world, including stations in numerous places that collect up-to-date data on infections, etc.

As usual, and I won’t mince words, YOU ARE FULL OF SHIT.

Read the book on immunology, read the book I gave on history of WHO, try to actually open your mind, that is, if you have one???

You cited a study showing Oral Polio vaccine caused increase in cases of non-polio acute flaccid paralysis. I debunked it with references. Just one example of how you cherry pick information. And no response from you, typical. I refute with references what you write and you ignore. No matter how many times shown just how wrong, how stupid you are, and you just continue.

I have now over 1,000 articles on current pandemic, together with what we know about coronaviruses. Have read around 250 of them and skimmed the rest. I have WHO, CDC, and several other COVID-19 websites bookmarked and regularly check them. And I am now going through new edition of immunology book and re-reading sections of an undergraduate text on microbiology that I actually did proof-reading and editing, my name in acknowledgments.

I guess you also have a negative opinion of the CDC, state, and local public health departments.

You and people like you turn my stomach.

@Joel – The chances of convincing people like CK are vanishingly small, but the references you give are appreciated by many others (including myself!) and most importantly allows anyone who is genuinely trying to understand the subject the tools to do so. Keep up the good work – although maybe try to keep more relaxed!

@ Joel,

It doesn’t matter if they “they corrected it post haste”. All’s that served to do is to make people say; “The WHO changed their minds AGAIN”.

I can’t stand social media but if you are not connected somehow, at least for observations sake; you don’t understand the damage that was done.

@ Joel:

You probably know as well as I do that CK is HIGHLY UNLIKELY to listen to your advice about reading research or text books: in fact, I doubt she’d follow Orac’s suggestions. She sets herself apart as being superior to all of SBM (and its supporters), which is merely artifice, propaganda and manufactured data whilst she has the Truth; I never diagnose anyone but you can probably come up with a few of your own in this case. She’s in the same category as Adams, Null, Wakefield, Bigtree, although for different reasons: they sell products and films, she sells herself and her supposed history

So what do we do with people like that? Frankly I don’t know: ignore, refute, ridicule, educate or use as a negative example.? I realise that there is a strong tendency to counter commenters’ misinformation so as to enlighten other readers. and not let BS STAND where innocent readers may assume it’s meaningful because no one answers back. A long time ago, I presented another adamant anti-vaxxer with a challenge, asking ” How likely is it that ALL THE WORLD- scientists, doctors, governmental agencies, researchers GLOBALLY are wrong, and you’re right?”” How likely is it that research for decades around the world is wrong about vaccines being safe OR that one researcher CHEATED?” Which is more likely- that thousands cheated, lied and covered up a scandal in a vast conspiracy OR that one guy fixed data? We could ask her the same: Why should we believe you? Why is your stance superior to decades of research and observation by thousands of medical, psychological and educational researchers? Why are your supporters parents who reject vaccines or people who sell pseudoscience? Aren’t there OTHER explanations for their beliefs that are based in psychological/ economic need rather than reality?

@ Christine Kincaid

As I pointed out, the WHO corrected any misleading claims almost immediately. On the other hand, we can look at Trump, despite being warned in January, ignored the scientists, not once; but over and over again. Credible accounts find that had he implemented the lockdown just two weeks earlier, 2/3 of the lives lost would have been saved. He did ban travel from China, well, not exactly, Chinese couldn’t enter U.S.; but returning Americans could without quarantine. And he even exported PPE. In addition, he publicly began telling us the virus wouldn’t reach the U.S., then it wasn’t all that dangerous, then over and over that we have it under control.

So, WHO corrects/clarifies immediately and the U.S. government’s response goes on for months. Also, it was Trump who shut down White House Pandemic advisory committee, cut funds to CDC and WHO before pandemic, ignored the Pandemic Protocol developed by Obama in 2016. No ones perfect; but compared to our government WHO is a role model. And one last thing, the AIDS pandemic that has taken millions of lives is mainly our responsibility. When AIDS first appeared our government did nothing, then later when the WHO developed programs to prevent its spread in Africa, we threatened cutting funding in a protest against handing out condoms. So far more lives have been lost, both from AIDs, then COVID-19 from actions and inactions by the U.S.

@ Joel,

Who was advising Trump? On January 21st, Fauci said:

“Obviously, you need to take it seriously and do the kind of things the (Centers for Disease Control and Prevention) and the Department of Homeland Security is doing. But this is not a major threat to the people of the United States and this is not something that the citizens of the United States right now should be worried about.”

… During his appearance on Newsmax TV.

On January 26th, Fauci says:

“The American people should not be worried or frightened by this. It’s a very, very low risk to the United States, but it’s something we, as public health officials, need to take very seriously.”

… During an interview with John Catsimatidis, a syndicated radio host in New York.

The CDC didn’t reverse it’s position on face masks until April 3rd. My God. I first wore a face mask on January 28th!

You are right a late response caused many covid deaths. International air travel should have been shut down by February 1st but who was advising Trump? I swear the WHO & the CDC wanted us sick.

@ Narad:

The situation can change Thank you.
That’s exactly what I’ve noticed monitoring woo-meisters: they leave out part of the statement or distort it in an important way so that it means something very different to the casual observer.
Little by little, these adjustments add up.
-btw- I hope you are doing better with your housing situation and health. Could you find some city services for housing? I don’t know your area but around here ( outside [redacted]) there might be partial assistance unless if you earn too much.

I don’t know your area but around here ( outside [redacted]) there might be partial assistance unless if you earn too much.

Oh, I’ve been on a waiting list for years, and I haven’t earned anything from other than odd jobs in about the same time. The real trick now is going to be refiling for SSDI without a fixed address.

@ Christine Kincaid

Wrong as usual. Yes, with Trump looking on he moderated his tone; but there is overwhelming evidence that he, the CDC, national security council and others had been trying to get Trump to act.

As for banning international travel, research shows doesn’t always work, better to screen people, even isolate for up to two weeks. As we’ve seen, Trump banned Chinese coming from China; but not Americans returning and didn’t ban travel from Europe or close border with Canada. In any case, evidence is that the virus was already in the U.S.

And your comment on Feds vs States/local just one more example of how stupid you are. It is called a pandemic for a reason, quite simply airborne viruses don’t pay attention to political boundaries

And, last time I looked we are one nation. During the Depression and Dust Bowl era, the wealthy states, through taxes, helped the poorer states, e.g., TVA, mosquito abatement to end malaria in South, help to Oklahoma, including monies for unemployed and farmers, agricultural experts that showed them how to grow crops, irrigate, etc. Interesting the hypocrisy of many Americans. The States that we’ve bailed out, are those who complain of taxes, want government off people’s backs; but really want other people to pay taxes to benefit them and want to impose their beliefs on others.

It continues to this day. New Gingrich bragged that his district had few on welfare; but failed to add that as Speaker of the House he got all kinds of government contracts to his district.

But, as usual, you find one quote from Fauci and ignore the overwhelming other evidence.

And the WHO warned of a deadly new virus early in January and that it might be person-to-person. Stop being a dishonest person, listen to what others right. What a STUPID STUPID thing to say that WHO and CDC wanted us to be sick.

It is you who are a paranoid sick moron.

Welp, my irony meter broke at Christine attacking people for inconsistent messaging and misspeaking.

@ Christine Kincaid

Note the following is from a Wikipedia article. I have a number of other independent articles that I doubled checked the accuracy of this article and note its extensive reference list.

Note the CDC issued it first public alert on January 8.
Note on January 10 the WHO warned of the risk of person-to-person transmission.
Note on January 14 The WHO recommended countries to take precautions due to the human-to-human transmission during earlier SARS and MERS outbreaks.
And note on January 18, Azar discussed with Trump who told him not to be an alarmist.

I should point out that when the WHO issued highest pandemic warning of pandemic novel H1N1 flu, turned out to have killed fewer people; however, higher percentage of young people. WHO was severely criticized and Director resigned. If they had not warned and it became a deadly pandemic, what then? Damned if they do and damned if they don’t.

Could the Chinese and WHO acted a week or two sooner? Maybe; but Trump still would not have done anything. He had already reduced funding to WHO and CDC, closed White House Pandemic Team, etc. You are tiresome. We had enough warnings that if Obama or Bush had been President we would have reacted appropriately. But you want to blame everyone; but our Government. Keep in mind that both South Korea and Taiwan, based on the early information provided by China, acted and have had the absolute lowest deaths per capita anywhere.

And I already responded to you; but you are either incredibly stupid and/or dishonest. I think both. Check out:
Joel A. Harrison, PhD, MPH
May 26, 2020 at 11:26 am

Timeline of the COVID-19 pandemic in the United States

Prior to January 19[edit]
On December 31, 2019, the U.S. Centers for Disease Control and Prevention (CDC) became aware of cases in China and began developing reports for the Department of Health and Human Services (HHS) on January 1.[68][69]
On January 3, CDC Director Robert Redfield was notified by a counterpart in China that a “mysterious respiratory illness was spreading in Wuhan [China]”; he notified HHS Secretary Alex Azar, who shared the report with the National Security Council (NSC). According to The Washington Post, warnings about the virus were included in the President’s Daily Brief in early January, an indicator of the emphasis placed on the virus by the intelligence community.[69][68]
On January 5, the World Health Organization (WHO) reported a “pneumonia of unknown cause” in Wuhan, China. The WHO advised against travel or trade restrictions at the time.[70]
On January 6, CDC Director offered in a letter to Chinese officials to send a team of CDC scientists to assist China. China did not accept the offer for several weeks, which delayed the U.S. access to the virus, important for developing diagnostic tests and a vaccine.[68] China did release genetic data on the new coronavirus on January 9.[71]
During the week of January 6, officials of the Department of Health and Human Services (HHS) convened an intra-agency task force including Redfield (CDC), Azar (HHS), and Anthony S. Fauci, Director of the National Institute of Allergy and Infectious Diseases.[68]
On January 7, Ohio claims to have the first COVID-19 patient per the data download at
On January 8, the CDC issued its first public alert about the coronavirus.[68]
On January 9, the WHO issued a statement naming the disease as a new coronavirus in Wuhan.[70]
On January 10, the WHO issued a comprehensive package of guidance to countries on how to test for potential cases.[72] By this date, the WHO warned of the risk of human-to-human transmission.[73][74]
On January 14, the WHO held a press briefing stating that their information suggested a possibility of limited, but not sustained, human-to-human transmission.[75] The WHO recommended countries to take precautions due to the human-to-human transmission during earlier SARS and MERS outbreaks.[73][74] The WHO also tweeted that “preliminary investigations conducted by the Chinese authorities have found no clear evidence of human-to-human transmission of the novel #coronavirus (2019-nCoV)”.[76] The head of China’s National Health Commission, Ma Xiaowei, confidentially provided a “grim” situation assessment to key Chinese health officials. The related memo said “human-to-human transmission is possible.” An investigation by AP News indicated that the reporting of a case in Thailand prompted the meeting, as well as the risk of spread with heightened travel during the Chinese New Year and various political considerations. However, the Chinese public is not warned until January 20.[77]
Beginning January 17, the CDC dispatched public health experts to screen incoming airport passengers at John F. Kennedy International Airport in New York City, San Francisco, and Los Angeles, adding monitors at Chicago and Atlanta in late January.[78]
On January 18, HHS Secretary Azar discussed the coronavirus outbreak with President Donald Trump, who criticized Azar for being “alarmist”.[68]
Joel A. Harrison, PhD, MPH
May 26, 2020 at 11:26 am
@ Christine Kincaid
You write: “It was obvious by January 13th. They waited until January 30th.”
The informed the world first few days in January that a novel deadly virus had broken out. Trump’s national security team notified Trump, etc. Keep in mind that when WHO issued pandemic warning in 2009 about the swine flu, which was a novel version and killing people, because it didn’t cause a huge number of deaths, WHO was accused of crying wolf and WHO director was forced to resign. So WHO did notify world early on of potential dangerous new virus. If they had issued higher warning and it didn’t pan out, what then? Damned if they do and damned if they don’t. As I wrote elsewhere, a few cases of deadly pneumonia won’t necessarily lead to discovery of a novel virus, only when a larger cluster develops.
I suggest, you evil moron, that you actually do a comprehensive search of the sequence of “warnings,” instead of focusing on what, as usual, confirms what you choose to believe. You are really a sickening despicable example of a human being. And I am dead serious. WHO carefully evaluated the information it received and passed it on; but China also directly passed it on. With hindsight one always has 20-20 vision, so, maybe WHO could have advanced its Jan 30 warning by a few days, maybe; but overwhelming evidence is that if Trump administration had actually acted on the information it received and even implemented measures one week earlier, 30,000 lives would have been saved, if two weeks early, perhaps 50,000 or more lives would have been saved, so it is Trump administration that rejected received information [Lazaro Gamio (2020 May 22). Lockdown Delays Cost at Least 36,000 Lives, Data Show. New York Times]. Trump worry about it affecting his re-election. Typical, Trump thinks only of himself.
For instance: WHO Timeline – COVID-19 at:—covid-19
And for details of when U.S. first aware, try Schwellenbach (2020 May 6). The First 100 Days of the U.S. Government’s COVID-19 Response at:
I’ve got plenty more. As I think I mentioned in a previous comment, since outbreak of COVID-19, I’ve downloaded well over 500 articles on coronaviruses in general and COVID-19, peer-reviewed journal articles, book chapters, news articles, etc. I’ve read over 100 carefully and skimmed the rest. In a previous post I also debunked claim that escaped from Wuhan lab with peer-reviewed journal articles.

There’s no good evidence for this, and it was shown conclusively in March that the nucleotide sequence of SARS-CoV-2 shows no sign of human manipulation.?


The best summary article is Anderson (2020). Basically, first, a 2015 study found literally 1,000s of variants of coronaviruses in bats (Manachery, 2015). It was found that 2.7% of population had antibodies to some of these strains (Wang, 2018). There is indications now that some of these viruses had been in people for more than a decade, ample time to mutate to easier transmission between people. The fact that the first case probably didn’t get it at the market means nothing. The market could have been an amplification place; that is, people could have been, as the 2.7%, randomly exposed to virus; but the market place represented a concentrated exposure. The Taiwanese study took the protein S-spike from bat coronoviruses, attached it to a harmless virus and found it capable of attaching to, among others, human cells (Chen, 2019). Finally, sequencing of the SARS-CoV-2 genome has found it close to several bat coronaviruses and even closer to one in pangolins (Anderson, 2020). Nature is quite good at mutations, so, either a few mutations enabled it to directly attack humans or, already in humans, it mutated to become more easily transmissible. This could also explain why the Chinese at first didn’t document human to human transmission; namely, those first getting it directly from bats and/or pangolins did transmit it easily; but further mutations and pandemic.

I would suggest anyone interested to get hold of each and every one of the following articles and read them CAREFULLY. Is it still possible it escaped from the Wuhan Lab. Anything is possible; but the odds against are extremely high. Anyone still pushing this has an agenda and it isn’t based on science.

[Note. Go to PubMed at: Type in complete title. Most have free pdf downloads; but a few just ABSTRACTS , some can be found by Googling Titles]

Anderson et al. (2020 Apr). The proximal origin of SARS-CoV-2. Nature Medicine; 26(4): 450-452.

Chen et al. (2019 Nov 22). Entry of Scotophilus Bat Coronavirus-512 and Severe Acute Respiratory Syndrome Coronavirus in Human and Multiple Animal Cells. Pathogens; 8(4).

Ge et al. (2013 Nov 28). Isolation and characterization of a bat SARS-like coronavirus that uses the ACE2 receptor. Nature; 503(7477): 535-538.

Guo et al (2020 Mar 13). The origin, transmission and clinical therapies on coronavirus disease 2019 (COVID-19) outbreak – an update on the status. Military Medical Research; 7(1).

Hu et al.(2018 Sep 12). Genomic characterization and infectivity of a novel SARS-like coronavirus in Chinese bats. Emerging Microbes & Infections; 7(1).

Liu et al. (2020 Feb 26). No credible evidence supporting claims of the laboratory engineering of SARS-CoV-2. Emerging Microbes & Infections: 9(1): 505-507.

Menachery et al. (2015 Dec). A SARS-like cluster of circulating bat coronaviruses shows potential for human emergence. Nature Medicine; 21(12): 1508-1513.

Menachery et al. (2016 Mar 15). SARS-like WIV1-CoV poised for human emergence. Proceedings of the National Academy of Sciences of the United States of America; 13(11): 3048-3053.

Qiu (2020 Mar 11). How China’s “Bat Woman” Hunted Down Viruses from SARS to the New Coronavirus. Scientific American

Wang et al. (2018). Serological Evidence of Bat SARS-Related Coronavirus Infection in Humans, China. Virologica Sinica; 33(1):104–107.
Zhou et al. (2020 Mar 12). A pneumonia outbreak associated with a new coronavirus of probable bat origin. Nature; 579(7798): 270-273.


Last sentence in first paragraph should read: “namely, those first getting it directly from bats and/or pangolins did NOT transmit it easily; but further mutations and pandemic.”


Just came across two more articles that COVID-19 likelihood overwhelming came from bats, not lab:

Schmidt C, Undark (2020 Jun 13). Coronavirus Researchers Tried to Warn Us: Before the pandemic hit, they struggled to get funding that might have hastened treatments for COVID-19. The Atlantic. Available at:

Cheng VCC et al. (2007 Oct). Severe Acute Respiratory Syndrome Coronavirus as an Agent of Emerging and Reemerging Infection. Clinical Microbiological Reviews; 20(4): 660-694. Available at:

Comments are closed.


Subscribe now to keep reading and get access to the full archive.

Continue reading