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Jan. 24 marks the one-year anniversary of a momentous but largely unnoticed event in the history of the Covid-19 pandemic: the first published report of an individual infected with the novel coronavirus who never developed symptoms. This early confirmation of asymptomatic infection should have set off alarm bells and profoundly altered our response to the gathering storm. But it did not. One year later we are still paying the price for this catastrophic blunder.

At least one of three people infected with SARS-CoV-2, the virus that causes Covid-19, do not develop symptoms. That’s the conclusion of a review we just published in the Annals of Internal Medicine. It summarizes the results of 61 studies with more than 1.8 million people.


But during much of the pandemic, fierce resistance — and even outright denialism — in acknowledging this not-so-typical disease pattern led to ineffective testing practices that allowed the pandemic to spin out of control.

On Jan. 28, 2020, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said, “In all the history of respiratory-borne viruses of any type, asymptomatic transmission has never been the driver of outbreaks. … Even if there’s a rare asymptomatic person that might transmit, an epidemic is not driven by asymptomatic carriers.”

This was a widely held view. On June 8, 2020, a senior official of the World Health Organization called asymptomatic transmission “very rare.”


To his credit, Fauci was among those who immediately criticized this remark. Based on epidemiological data that had become available since his earlier comments, he said it was “not correct” to characterize asymptomatic transmission as rare.

In June, when we published a report of 16 cohorts with sizable proportions of asymptomatic infection and suggested that it might play a role in the progression of the pandemic, several researchers wrote letters to the editor demanding that our paper be retracted.

Today, the best evidence suggests that about half of Covid-19 cases are caused by infected people who do not have symptoms when they pass on the virus. These symptom-free spreaders are roughly divided between those who later develop symptoms, known as pre-symptomatic individuals, and those who never develop symptoms.

While the importance of asymptomatic infection in understanding Covid-19 has been surprising to some, infectious disease experts have long known that infection without symptoms is common in many illnesses. More than 90% of people infected with poliovirus have no symptoms. And about 75% of influenza infections have been estimated to be asymptomatic. Yet these important precedents have largely been ignored.

Asymptomatic coronavirus infection is not necessarily benign. Several studies have reported abnormal lung scans in those infected without symptoms, as well as myocarditis, a type of heart inflammation. The long-term health implications of asymptomatic infection aren’t known.

Even though knowledge about asymptomatic infection has greatly evolved, tactics for combating the pandemic have not. It is now obvious that testing only those with symptoms, as was common early in the pandemic, is a mistake because it ignores the invisible legions of infected people who have no symptoms. But it is not enough to merely increase the number of tests. The problem is that current testing practices are ill-suited to detecting and containing asymptomatic infection.

Virtually all of the coronavirus testing performed in the U.S. looks for the genetic material of the virus using the polymerase chain reaction (PCR). It requires expensive equipment and trained technicians. Results are typically returned days — sometimes even weeks — after the test. That means people learn they have been infected with SARS-CoV-2 long after they may have passed the virus to others. Testing becomes more about accounting — tallying the number of detected infections — than about containing the spread of the virus.

What’s needed is a pivot to a different type of testing. Antigen tests, which look for a bit of coronavirus protein, cost just a few dollars each and can yield results in minutes. Like home pregnancy tests, they require minimal instruction. Antigen tests are ideal for spotting people who are infectious, rather than those who may be long past the infectious phase of Covid-19, or who harbor such low levels of the virus that they are unlikely to infect others.

Inexpensive rapid home tests would help infected people isolate themselves before they could spread the virus. Frequent testing — at least several times per week — is essential, as demonstrated by successful testing efforts at some universities, which have enabled students to return to campus. A new focus on self testing, in combination with financial assistance and perhaps even temporary housing for isolation, would directly address the problem of asymptomatic infection.

The rollout of Covid-19 vaccines brings with it the risk of a new wave of asymptomatic infections. The two vaccines authorized by the Food and Drug Administration have been proven to prevent illness, but not asymptomatic infection. Even after vaccination, the coronavirus may still temporarily take up residence in the lining of the respiratory tract, making it possible to infect others. Preliminary results from one vaccine trial seem encouraging, with an apparent two-thirds reduction in asymptomatic infection after the first dose. But many other studies are underway.

There is no time machine that would allow us to return to Jan. 24, 2020, and make the plans we should have made, which would have acknowledged the importance of asymptomatic infection. But it is not too late to recognize the blunder and move aggressively toward testing practices that will help end the pandemic.

Daniel P. Oran is a member of the digital medicine group at Scripps Research Translational Institute, of which Eric J. Topol is founder and director.

  • Thank you. Please advise the WH that in person instruction in schools is in effect sentencing millions to a herd immunity by infection scenario which will result in many more deaths.

  • How exactly do you follow the science, when their isn’t any?
    Everything here is turned into the political swamp.
    And everything about is polluted.
    Many Doctors and health professionals are far too willing to adopt virtually any opinion for a gig as an expert in the mainstream media.
    And that’s about where we’re at America. And it’s not a good place.

  • How exactly do you follow the science, when their isn’t any?
    Everything here is turned into the political swamp.
    And everything about is polluted.
    Many Doctors and health professionals are far too willing to adopt virtually any opinion for a gig as an expert in the mainstream media.
    And that’s about where we’re at America. And it’s not a good place.

  • Asymptomatic transmission is a hallmark of coronaviruses. Epidemiologists have long feared a coronavirus pandemic for this exact reason. Two weeks of being a contagious host before symptoms is normal for coronaviruses. For the flu this period is typically two days or less. The flu contagious period occurs 80% during the symptomatic period. The coronavirus contagious period can be as much as 80% during the asymptomatic period. A coronavirus was even chosen for the “Center for Health Security” “Event 201” exercise in October 2019 (somewhat prescient) . Scientists already knew that coronaviruses were spread by asymptomatic hosts. Half of all “common cold” cases are coronaviruses, coronaviruses are not something completely new to us. Dr. Fauci’s quote, taken out of context is true only because we have not ever had a coronavirus pandemic. The coronavirus has been an irritant, not a wide-spread killer. This entire pandemic has been an exercise in willful disregard for science and evidence. Countries that listened to their scientists did much better than countries that did not.

    With regard to testing approaches: This article should reference this country’s one major successful testing program if it is going to talk about what we should be doing versus what we are doing with respect to testing:

  • Like we had a choice? No one is going to take action based on one case report, even if supported by other virus history. So yes, we missed that early opportunity. But as things rolled out, it would not have made a difference.

    When asymptomatic transmission became clear, initial CDC guidelines addressed it, then reversed under political pressure but eventually again came out with testing and mask recommendations reflecting the reality. Testing supplies still lagged the clear need. Lacking clear national mandates, states took their own directions even up til the present. Confusion and denial still reign.

    Yes, there was a lag from the first case report of asymptomatic transmission until clear actionable information. But to state it was a blunder is inaccurate. A blunder implies it was a mistake. The Trump administration and focused intentional misinformation takes it from a mistake to a crime. Our very scientists were suppressed and deliberately taken out of the loop.

    Your article presupposes a rational, functioning society with strong leadership looking at the evidence. In which case, yes, an early opportunity was missed.

    It wasn’t a blunder we have to recover from, it is criminal suppression of the science. And yes, there is a new frontier to face… what do we know about transmission after vaccination, and how will we shape our responses. So stop with the blunder stuff, and go with the science and what we do know and what we don’t and how to go forward.

    There is definitely room for articles which point out possible problems post vaccination and where we are going, but STOP the sexy titles and the tabloid crap.

    • Points exceptionally well taken and well expressed. In support of your objection to the word “blunder”, please see also my comment, the first in this series, below. As noted by another reader, it’s the attitude underlying this word that is causing the biggest problem in this country.

    • The split narratives between the high IQ science based one by Cuomo and the low IQ factless one by Trump was intentional. The lower IQ faction of our electorate was too prone to panic and violence besides being naturally more susceptible to opposition disorders. Not one town nor supermarket was taken by armed militants. We still face the obvious choice of not enforcing mandates upon the violent and subjecting healthcare workers to harm. More harm is done if a medical professional is assaulted or killed than an individual so prone to violence ignoring his own safety. Those critical national security threats are more pressing than your need to have a factual presentation for our chief executive. You should not have been in the children’s section to even care what Trump said.

  • Remember, not all people are honest about having symptoms; at work , unless you are dying, you can not be excused (nurses ). And not everybody wants to be tested, denial, or fear of knowing.
    We all learn, nothing perfect , no algorithm to really follow.

  • You sacrifice accuracy in return for speed with antigen tests. Otherwise, you raise valid points. You correctly pointed out that the focus in most areas has been on testing symptomatic people or those known to have been exposed. The goal of this tactic would be to identify infected people without wasting a lot of tests on people who are not infected. A high positivity rate would indicate some level of success in achieving that goal. It seems more than a little bizarre, then, that state and local governments are using a high positivity rate as an indicator that mitigation efforts are insufficient. The message to county health officers seems to be “Do your best to find the infected people, but if you do a good job of this we’ll force you into lockdown.”.

  • As someone that bought into the quarantine in the start. I think we are going to find that Covid 19 has already infected a majority of the population. In retrospect, I don’t believe that a Virus that has even entered a closed society like North Korea, can be controlled in a open Western environment.

    • I agree with your assessment. As a scientist working at a healthcare institution in NYC, I believe that the reason NY and NJ were not hit hard with the second wave is that most of use have already been exposed to the virus. Based on some of the antibody studies I have seen, I also think the numbers of asymptomatic cases, as well as the numbers of people who have some level of immunity because of exposure to other coronaviruses, have both been vastly underestimated. I think it is somewhat arrogant of us to think we can control exposure to an airborne virus using ineffective masks and social distancing. We are going to have to live with this one, and please do not interpret this as callous, but we are rather lucky this isn’t more deadly than it is.

  • Your points are so valid and your overall argument is woven together tightly, but your overall tone and word choice are unnecessarily inflammatory and represent, to use your favorite word, a “blunder”. This relentless griping from a bunch of know-it-all fault-finders has gone from merely annoying to frankly counterproductive. You gripe when a vaccine is developed too quickly and then you gripe when it’s not rolled out quickly enough. You gripe when perfect clarity of every unknown isn’t perfectly translated into perfect policy and then, if it is, you gripe that it wasn’t done sooner. You will likely gripe that these observations are unfair and unfounded. This incessant blame-laying and scapegoating is beneath you, and you know it. Let the power of your message lie in the resonance of the major chords, not the dissonance of the minor chords.

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