A smart man once told me he uses electric toothbrushes because that's what the dentist uses for professional cleanings (1). It's a great bit of simple logic at work, and during the pandemic I've found that applying this style of analysis encourages the right kind of behavior. The best reason to wear a mask was that the hospital system where I work told everyone to wear a mask. When it comes to making a smart decision, it's rarely a bad idea to mimic the experts.
However, mimicry and understanding are two separate questions, and I admit at times it takes me a little longer than I'd like before I fully comprehend the underlying thought process. Social distancing has been a great example. Initially, the six feet apart concept was crystal clear, but as the lockdown progressed I became slightly confused. For example, it didn't seem like any of the grocery stores I went to made a special effort to keep everyone six feet apart, whether it be by removing extra display tables in the middle of a narrow aisle or by closing checkout registers that fell within sneezing range of a neighbor. I also noticed nurses waiting outside a local takeout option who, despite being fully masked and gloved, were chattering away in line within touching distance of each other. Based on what I knew these people and places should know better, unless of course they did, by having access to better information than me.
I soon learned about a public health method called contact tracing, a process where those who were in 'close contact' with a sick person would be notified and, in the specific example of COVID-19, instructed to self-quarantine for two weeks. The guidelines for 'close contact' added a new layer to my thinking - in addition to being within six feet of the infected person, a close contact also needed to spend at least fifteen minutes inside that six foot radius. My initial reaction was a mixture of illumination and outrage - so this is the top secret information that informed my prior observations! I felt like a bit of a sucker to be honest, not just because of the general fact of lockdown, but for all those moments in March when someone momentarily coming within six feet of me left me nauseated.
I wondered, why didn't our officials suggest we remain six feet apart only if the interaction would exceed fifteen minutes? It should be fairly simple to keep track of fifteen minutes and, unlike with six feet, I suspect most of us would naturally err on the side of caution (based on my walks and runs, I don't think most of my fellow Bostonians could measure out six feet, even using two yardsticks). We often casually toss around 'fifteen minutes' to mean a short period of time, but fifteen minutes is a fairly long time. Think of the most annoying pop song you know - I bet you can listen to it four times in fifteen minutes. At first glance, a mandate to stay six feet apart with exceptions for interactions less than fifteen minutes seems manageable to me.
Of course, as noted above I know that sometimes I need a little more time to come around and understand the full story, so I remained patient before making any rash adjustments to my distant behavior. Although the time element in contact tracing guidelines were hard to reconcile with the lack of an equivalent in social distancing recommendations, I tried to think about it from the public health perspective. What I soon realized was that prior to the pandemic, I came within six feet of people all the time, but I rarely had 'close contacts'. Work meetings, commuting on the subway, and the occasional public event were likely sources of close contacts, as were almost all social outings. But this would never be more than a couple of people per day except for the rarest cases, and on average most weeks likely passed without more than ten close contacts. However, it was impossible to answer the question of 'within six feet'. The subway trip alone was enough to break an abacus - I could easily come within six feet of at least a hundred people in ten minutes. These could be for just a moment, certainly, but six feet is six feet.
I think this was when it made sense to me. I feel contact tracing is a little overblown, but part of the issue is that it's a highly specialized option within a relatively spare toolbox. It's certain to be overused because as one of few available tools it will be applied to any problem even vaguely resembling an infectious disease outbreak. However, I recognize my opinion on contact tracing is almost as relevant as my opinion on Ricky Rubio's shooting ability - I come up Mount Stupid so fast I get the bends, but God help me as I stumble back down. When I say "I don't think contact tracing works..." it means two weeks later I'll say "...because others have failed to use it correctly, or misapplied the method to communities where everyone has hundred of close contacts."
In this case, what I realized during my proverbial two weeks is that contact tracing won't work in two situations, both of which fit the example of an infected person saying "well, I was on the Green Line between Arlington and Brookline Village during rush hour." The first issue is that you might spend fifteen minutes next to some stranger you'll never be able to identify and therefore cannot reach via contact tracing. This isn't good, but if it's just one person you can cross your fingers. The second issue is less obvious and might require some adjustment in terms of the exact numbers, but it's probably more concerning from the public health perspective - fleeting interactions add up but are impossible to break back down. Think of it this way, if an infected person coughs or sneezes, someone within six feet might get sick, and in terms of the virus it really doesn't matter if you know that unlucky person. In other words, whether it's a revolving door of many commuting strangers or just one close friend, the risk of transmitting the virus to 'a person' is related only to whether another person is within range. The challenge of this close contact being a 'composite person' is of course the same as stated earlier - how do you contact all of those people to say "hey, there is a 1/x chance you are sick"? You can't, and even if you did get them most of them, it would take so long that anyone infected likely would have passed the virus to someone else.
The first step to using contact tracing is to ensure infected people can reliably identify close contacts, and in the case of this pandemic that meant getting people to stop doing things like riding the Green Line that would strip contact tracing of its power. Since the start of my 'stay home' mode, I have had exactly zero 'close contacts' per the above definition, though maybe a couple of close calls would make the cut if we must be overly cautious (as we should be). But the other part is that I haven't had any 'composite close contacts', a fifteen minute period where I've been within at least one other person. For me, staying home has been enough to cut out the risk, and if I were to become infected in this current moment I could describe my close calls and help public health officials make an informed decision without complicating matters with my admission that I rode the subway the prior night. This feels about right. I still sense that social distancing requirements are a bit much in terms of stopping the spread, but that's like complaining that the car isn't moving while filling up the gas tank, or that the electric toothbrush isn't filling the cavity.
Footnotes
1. I just bought a year's supply today - six, in two packs of three
Despite my admiration for the analysis, I don't use an electric toothbrush. Part of the issue is that I stubbornly retain a general tendency to value technique over tools, and feel that with the right brushing technique I get the same results. There is also a slight logical fallacy - the right frame is to ask whether all dentists self-brush with the electric option, since this is the relevant behavior, but as noted in the prior sentence adjusting the question wouldn't change my commitment to the old school toothbrush.
