Dr Jonathan Smith

As an in­fec­tious dis­ease epi­demi­ol­o­gist, I feel moral­ly ob­lig­at­ed to pro­vide in­for­ma­tion on what we are see­ing from a trans­mis­sion dy­nam­ic per­spec­tive and how it ap­plies to the so­cial dis­tanc­ing mea­sures. Like any good sci­en­tist, I have no­ticed two things that are ei­ther not well ar­tic­u­lat­ed or not present in the “lit­er­a­ture” of on­line me­dia. (I have al­so re­lied on oth­er in­fec­tious dis­ease epi­demi­ol­o­gists for peer re­view of this piece.)

Specif­i­cal­ly, I want to make two as­pects of these dis­tanc­ing mea­sures very clear and un­am­bigu­ous.

First­ly, this virus is with us no more than two years, there­fore, we are in the very in­fan­cy stages of this epi­dem­ic’s tra­jec­to­ry. That means that even with these mea­sures in place, we will see cas­es and deaths con­tin­ue to rise glob­al­ly, na­tion­al­ly, and in our own com­mu­ni­ties. This may lead some to think that the so­cial dis­tanc­ing mea­sures are not work­ing. They are. They may feel fu­tile. They aren’t. You will feel dis­cour­aged. You should. This is nor­mal in chaos. This is the nor­mal epi­dem­ic tra­jec­to­ry. Stay calm.

The en­e­my we are fac­ing is very good at what it does; we are not fail­ing. We need every­one to hold the line as the epi­dem­ic in­evitably gets worse. This is not an opin­ion. This is the un­for­giv­ing math of epi­demics for which I and my col­leagues have ded­i­cat­ed our lives to un­der­stand­ing with great nu­ance, and this dis­ease is no ex­cep­tion. Stay strong and in sol­i­dar­i­ty know­ing that what you are do­ing is sav­ing lives, even as peo­ple con­tin­ue get­ting sick and dy­ing. You may feel like giv­ing in. Don’t.

We need every­one to hold the line as the epi­dem­ic in­evitably gets worse. This is not an opin­ion. This is the un­for­giv­ing math...

Sec­ond, al­though so­cial dis­tanc­ing mea­sures have been (at least tem­porar­i­ly) well-re­ceived, there is an ob­vi­ous-but-over­looked phe­nom­e­non when con­sid­er­ing groups (that is, house­holds) in trans­mis­sion dy­nam­ics. While so­cial dis­tanc­ing de­creas­es con­tact with mem­bers of so­ci­ety, it, of course, in­creas­es con­tact with­in a group (that is, fam­i­ly). This small and ob­vi­ous fact has sur­pris­ing­ly pro­found im­pli­ca­tions on dis­ease trans­mis­sion dy­nam­ics.

The ba­sic me­chan­ics of this math­e­mat­i­cal prin­ci­ple dic­tate that even if there is on­ly a lit­tle bit of ad­di­tion­al con­nec­tion be­tween groups (i.e., so­cial din­ners, play­dates, un­nec­es­sary trips to the store, et cetera), the epi­dem­ic like­ly won’t be much dif­fer­ent than if there was no mea­sure in place. The same un­der­ly­ing fun­da­men­tals of dis­ease trans­mis­sion ap­ply, and the re­sult is that the com­mu­ni­ty is left with all of the so­cial and eco­nom­ic dis­rup­tion but very lit­tle pub­lic health ben­e­fit.

You should per­ceive your en­tire fam­i­ly to func­tion as a sin­gle in­di­vid­ual unit: If one per­son puts them­selves at risk, every­one in the unit is at risk. Seem­ing­ly small so­cial chains get large and com­plex with alarm­ing speed. If your son vis­its his girl­friend, and you lat­er sneak over for cof­fee with a neigh­bour, your neigh­bour is now con­nect­ed to the in­fect­ed of­fice work­er that your son’s girl­friend’s moth­er shook hands with. This sounds sil­ly, it’s not. This is not a joke or hy­po­thet­i­cal. We as epi­demi­ol­o­gists see it borne out in the da­ta time and time again. Con­verse­ly, any break in that chain breaks dis­ease trans­mis­sion along that chain.

This out­break will not be over­come in one grand, sweep­ing ges­ture, but rather by the col­lec­tion of in­di­vid­ual choic­es we make in the com­ing months.

In con­trast to hand-wash­ing and oth­er per­son­al mea­sures, so­cial dis­tanc­ing mea­sures are not about in­di­vid­u­als, they are about so­ci­eties work­ing in uni­son. These mea­sures al­so re­quire sus­tained ac­tion be­fore re­sults are ev­i­dent. It is hard (even for me) to con­cep­tu­alise how on a pop­u­la­tion lev­el “one quick lit­tle get to­geth­er” can un­der­mine the en­tire frame­work of a pub­lic health in­ter­ven­tion, but it can. I promise you it can. I promise. I promise. I promise. You can’t cheat it. Peo­ple are al­ready itch­ing to cheat on the so­cial dis­tanc­ing pre­cau­tions just a “lit­tle” — a short play­date, a quick hair­cut, or pick­ing up a need­less item from the store. From a trans­mis­sion dy­nam­ics stand­point, this very quick­ly recre­ates a high­ly con­nect­ed so­cial net­work that un­der­mines much of the good work our com­mu­ni­ties have done thus far.

This out­break will not be over­come in one grand, sweep­ing ges­ture, but rather by the col­lec­tion of in­di­vid­ual choic­es we make in the com­ing months. This virus is un­for­giv­ing to un­wise choic­es. As this epi­dem­ic con­tin­ues, it will be easy to be drawn to the idea that what we are do­ing is not work­ing and we may feel com­pelled to “cheat” with un­nec­es­sary breach­es of so­cial dis­tanc­ing mea­sures. By know­ing what to ex­pect, and know­ing the crit­i­cal im­por­tance of main­tain­ing these mea­sures, my hope is to en­cour­age con­tin­ued com­mu­ni­ty spir­it and strate­gis­ing to per­se­vere in this time of un­cer­tain­ty.

Jonathan Smith, a lec­tur­er in epi­demi­ol­o­gy at Yale Uni­ver­si­ty, is com­plet­ing his PhD in epi­demi­ol­o­gy at Emory Uni­ver­si­ty. His re­search fo­cus­es specif­i­cal­ly on dif­fer­en­tial trans­mis­si­bil­i­ty of in­fec­tious dis­eases un­der var­i­ous pop­u­la­tion-lev­el and in­di­vid­ual-lev­el con­trol mea­sures.

This piece was first print­ed on WBUR: Boston Uni­ver­si­ty

OF NOTE: Dr Jonathan Smith orig­i­nal­ly wrote the piece as a let­ter to his lo­cal neigh­bour­hood of about 50 fam­i­lies. It struck a chord, and his neigh­bours be­gan shar­ing it wide­ly with­in their own net­works. Short­ly af­ter, and many tens of thou­sands of email for­wards lat­er, it went vi­ral. Dr Smith has gra­cious­ly grant­ed per­mis­sion to re­post the piece.