On Wednesday the Centers for Disease Control and Prevention announced a suspected case of COVID-19 in a patient who met none of the screening criteria for the disease. There was no travel to areas known to have cases, and no exposure to any sick persons suspected of or confirmed to have the virus. The patient is currently being treated at UC Davis Medical Center in California.
Overnight, this news raised the global pitch of coronavirus fever even higher. That’s understandable—the coronavirus seems even sneakier than before, and the risk even higher than ever. But when I looked at this, I had a different thought: Might this case actually be a good thing?
Here’s why it would be: Most public health officials now feel that widespread infection outside of the current hot zones like China and South Korea is no longer a matter of if but when. Containing the virus is likely impossible. So the next question is: Just how bad will the cases here be? In China, the death rate has been reported as zero in children under 10 and very low, 0.2 percent, in healthy adults. Unfortunately, the rate is far higher, as high as 14.8 percent, in the sick and elderly (though as is always the case in outbreaks like this, it is hard to know how many of these older and often chronically ill hospitalized patients died with COVID-19, not of COVID-19). The reported overall death rate of 2 percent is essentially a weighted average of these numbers.
So what does the case of a young and otherwise healthy patient contracting the disease despite no obvious exposure to a contagious source patient imply? That there are likely many asymptomatic cases in our communities already. Asymptomatic transmission has already been reported in China. In the first reported case, the source patient transmitted the infection to others but never became sick herself.
If this turns out to be common, it’s a good thing. It implies that the case fatality rate—the number of deaths divided by the number of infections—of this novel coronavirus is likely to be far, far lower than the reported statistics.
It’s worth parsing that coronavirus 2019-nCoV is the virus that causes the syndrome of respiratory symptoms now called COVID-19. The number of people who carry the 2019-nCoV virus is not equal to the number of people who develop COVID-19. These should be thought of as distinct entities. Only a subset of patients with the virus will ever develop COVID-19. We do not yet know how many infected patients go on to develop the symptomatic syndrome itself. But the more people who have the 2019-nCoV virus but do not develop the symptomatic COVID-19 syndrome itself, the less dangerous we can conclude it is for most people to contract it. Many may walk around and not notice.
While that may sound like a bunch of Typhoid Marys are walking around unknowingly infecting people, the assumption we have to make is that a high number of people will eventually be exposed to the virus anyway. If there’s one thing that’s clear so far, it’s just how contagious this virus is. So the fact that exposure might come sooner—because of asymptomatic carriers transmitting it in their communities—doesn’t make the disease any worse. It does suggest that not everyone will become sick from the virus and that the case fatality rate is likely far lower than the rates reported so far.
To be fair, it’s likely that both the number of cases and the number of fatalities is currently being underreported. We already have preliminary data suggesting that this is true for the number of cases. It’s less apparent that the number of deaths is being underreported. That’s not because of any conspiracy, but rather because of logistics. If there are asymptomatic cases, or if someone has a mild case in an area that isn’t known to have the virus, those cases are not likely to have been recognized. This is why the CDC originally rejected UC Davis’ request to test the individual now thought to have contracted the virus without a known exposure.
Meanwhile, unexplained deaths are harder to ignore. Even if a few people had died of an otherwise unexpected or unexplained infection in the United States, the CDC would have noticed it, using the same surveillance system it used to detect a relatively small number of cases of “vaping-associated lung injury” (which we now know was due to a particular additive to black market devices, not vaping itself). Yes, we are being watched by the CDC—and have been since the anthrax scare of 2001. I’m grateful, and you should be too.
While the presence of asymptomatic carriers should be reassuring for the young and healthy among us, it is also a stark reminder that our primary responsibility as citizens and neighbors is to do whatever we can to decrease spread of all infections, especially to vulnerable individuals, including older patients and those with serious medical problems like coronary artery disease, diabetes, chronic respiratory illnesses, and cancer. That of course includes things like hand-washing and staying on top of vaccination schedules. Wearing masks without attending to these other precautions misses the point, which is that most infections spread through lapses in hand hygiene and close contact. If COVID-19 panic finally teaches us to focus on the right things and to better adhere to those recommendations, in the long run this novel coronavirus might help us save more lives in our communities—for all contagious infections—than it ever directly kills.
The opinions expressed in this article are solely those of the author and do not reflect the views and opinions of Brigham and Women’s Hospital.