COVID-19: Testing, Testing 1, 2, 3
Updated: Mar 26
“When my information changes, I change my mind. What do you do?”
John Maynard Keyes
It’s hard to believe that less than four months have passed since COVID-19 emerged in Wuhan, China. By now it seems to have sucked the oxygen out of virtually every aspect of our lives and tragically for many that’s not a metaphor. While everyone has been on a steep learning curve, the good news is that an amazing amount already has been learned by scientists, public health officials, and leaders in many other crucial disciplines that is being applied to a rational strategy to defeat SARS-CoV-2, the cause of COVID-19.
One thing that’s become clear is that testing for the virus is a key weapon in our armamentarium. But there’s been much confusion about the test and why and how it should be used. The goal of this Germ Gem is to clear up this confusion.
First, some definitions. Believe it or not, infectious diseases specialists often argue about how to define an infection vs an infectious disease. I will give you the definitions that I think are most relevant to the COVID-19 pandemic.
An infection describes any established relationship between a germ (microbe) and a host (like a human). It doesn’t tell you anything about the nature of that relationship: good, bad, or indifferent. (By the way, most are good or indifferent.) So by this definition, we are all infected from head-to-toe, or in the case of the gastrointestinal tract—where about 40 trillion bacteria and 380 trillion viruses reside—from the tip of your tongue to the other end of your alimentary tract. Some experts refer to this kind of relationship as colonization.
An infectious disease, on the other hand, refers to a relationship between a microbe and a host that gives rise to illness (dis-ease). The microbe thereby is called a pathogen, like the coronavirus, SARS-CoV-2. These are the kinds of relationships that receive the most attention from infectious diseases doctors. We usually don’t care about the colonizers.
It’s important to know something of this aspect of basic microbiology because it sheds light on some of the confusion arising from how cases of COVID-19 are reported. If asymptomatic infections (referred to as undocumented infections in some countries) are lumped together with patients who are ill (that is, those with an infectious disease), the case numbers will be high.
Enter SARS-CoV-2. This pathogen provokes illness ranging from a mild to fatal disease. But it more commonly (and fortunately) just colonizes the upper respiratory tract and causes an asymptomatic infection. What appears to be unique about people with asymptomatic SARS-CoV-2 infections and why we must care about them is becuse they can transmit the virus to others, who may not be so lucky and come down with a full-blown case of the disease. This is why when people are identified as testing positive for SARS-CoV-2 they are (or should be) quarantined, even though they aren’t sick.
What is the nature of the test? The technique most commonly used to identify SARS-CoV-2 is called RT-PCR (Reverse Transcriptase - Polymerase Chain Reaction). It’s a molecular test that detects genetic sequences (RNA) of the virus. It is exquisitely sensitive, picking up only tiny amounts of the virus from a swab. It is highly specific, that is, it only picks up this coronavirus, and generally, results are available within several hours. But innovations are underway that will lead to point-of-care testing giving immediate results.
Who should be tested? As I’m sure you know, the United States was caught flat-footed on having the capacity to test everybody who should be tested. So for now, using the test to establish the diagnosis of sick people with respiratory tract symptoms (cough, shortness of breath) or fever is the top priority. But it also should be used to test contacts of people with known COVID-19 to help with decisions about quarantining. This strategy will help us better understand how the virus is spread and the benefits of isolating (quarantining) people who aren’t sick but nonetheless can transmit SARS-CoV-2.
So, what do I recommend regarding getting tested? If you have symptoms of COVID-19 that I’ve mentioned or have come into contact with someone who is known to be test-positive (suffering with COVID-19 or asymptomatic), call your doctor and follow their recommendations. Otherwise relax, don’t overburden an already stretched thin healthcare system.
What have we learned from testing outside the U.S.? While the bad news is that COVID-19 is now global (i.e., a pandemic), the good news is that the information needed to combat SARS-CoV-2 is constantly streaming in from all over the world. Thus decisions in the U.S. are informed by data and experiences from places such as China, Singapore, Hong Kong, and South Korea, where the disease is waning or was managed aggressively from the get-go, as well as from countries like Italy, which is caught in the jaws of the disease.
Data emerging from Iceland is particularly valuable. Iceland’s government has tested a higher proportion of its citizens than anywhere else in the world. While the figures are based on only a small sample of the data that ultimately will be accumulated, several trends are highly revealing.
Of those with positive tests, whether they were asymptomatic or ill, at least half had contracted the virus while traveling abroad. And of those with positive tests about half were from asymptomatic people. From their data, and those cited from the small northern Italian town of Vo, where they have been testing aggressively, it was suggested: “The testing has provided evidence revealing that a significant portion of those who catch the disease [virus] do so with no or mild symptoms—and confirmed multiple pieces of research that have shown that asymptomatic individuals contribute to the transmission of the disease [virus] in great numbers.”
Importantly what this means is that decisions can be based on evidence coming from all corners of the world. And that it supports what our leaders at the National Institute of Allergy and Infectious Diseases—in particular their director, Tony Fauci, and many authorities at the World Health Organization and Center for Disease Control and Prevention are telling us—we need to be testing, testing, testing.
What does this all mean? To me, at least, it is now clear that for every patient who has the infectious disease called COVID-19, there are five to ten people with asymptomatic infections (tested positive with no disease). This is good news for the latter group of people because they’re not ill. But even though they have no symptoms, they should be quarantined because they can transmit the virus to others, including those at highest risk of developing serious disease: the elderly, those with a compromised immune system, or with chronic heart of lung disease, or diabetes.
Are we on the right path? I also believe the evidence so far supports the current strategy laid out by our public health experts. And if new evidence arises suggesting the strategy should change, they’ll do so. I hope your confidence, like mine, is bolstered by the science that is supporting our “troops.” While SARS-CoV-2 is a wily enemy, it will be defeated.
Finally, as I’m sure all readers will agree, COVID-19 is testing us: our courage, resilience, compassion, and creativity. I’m inspired by the outbreak of countless acts of kindness I’ve witnessed recently. While the pandemic is keeping us apart physically, it is strangely drawing us together. On that note, I recommend visiting this internet site sent to us by very close friends in The Netherlands: Beethoven’s 9th Symphony (“Ode to Joy”) performed by musicians of the Rotterdam Philharmonic—at home! Whether you like classical music or not, this performance should lift your spirits.