Defeating Covid-19 and returning to a world we once again recognize may have less to do with biology and epidemiology and more with physics.  To be clear, viruses have unique and at times confounding characteristics that can be very difficult to assess, especially as they continually mutate, playing a biological game of hide and seek.  We must further acknowledge that our scientific and medical community is doing everything it can, motivated by both public policy supports and economic incentives, to introduce vaccines and therapeutic treatments to defeat Covid-19.  But, victory over this insidious disease will come sooner if we focus on what we can affect today—the physics of Covid-19—that include two principal factors: the density and flow of human beings.

Humans play two viral roles: hosts and vectors.  We host the virus as its vessel of life and we transmit the virus as its method of transportation.  Without access to our warm nurturing and mobile bodies, it dies.  There are, therefore, two and only two elements of physics we must interrupt to defeat Covid-19: the density and flow of humans.  And, as is often the case, the data tells the story.  Look at the data and the maps they illustrate and the big numbers and big red blobs confirm the hypothesis: places with both high density and rapid flows of humans are hit the hardest, like New York City.  Meanwhile, the Dakotas appear as if they are sitting this pandemic out.  Admittedly, some of this gap in viral incidents can still be blamed on a lack of testing, but that gap is shrinking as more testing occurs.  In my own county of Ouray, Colorado, our commissioners and public health officials continue to tout “no confirmed tests in the county!,” which amounts to little more than a head-in-the-sand proclamation due to a lack of testing.  It’s an easy claim when one’s eyes are shut that dangerously lulls the community into a false sense of immunity and careless behaviors.  As humans, we are hosts and vectors just as humans are in large cities.  But, what we have going for us is a lack of density and flow.

In an attempt to gain more materiel support for New York, Governor Andrew Cuomo asserted, watch out America, “We are your future.”  As welcome as Cuomo’s veracity and tenacity are when compared to our president, his assertion is false.  Few places in the United States have the density and flow of humans that the New York metropolitan area does.  The New York City metropolitan area has around 24 million people in 3,450 square miles, or 7,000 people per square mile.  By comparison, the State of Texas has around 28 million people occupying 268,597 square miles, or 104 people per square mile.  New York City then has 67 times higher population density than Texas and, understandably, has (currently) 32 times more confirmed Covid-19 cases.  To get a sense of flow, historically Texas has 255 million visitors while New York City has 65 million, or 4x more visitors in Texas.  This flow multiple in Texas is, however, spread over a vastly larger geographic area, which partially explains a less than 4x adjustment to expected viral infections in Texas.  Density and flow must be considered together, as a dynamic duo of physical impacts.  But, it does (along with levels of current testing and medical interventions—much higher in New York City than Texas) help explain why there are (only) 32x more cases than the 67x suggested by the density data alone.  I recognize this back-of-the-napkin analysis will be cringe-worthy to some epidemiologists who would argue for much deeper analysis, but they might also recognize that the availability and quality of data today does not yet exist to satisfy their desire for a broader and deeper plunge.  Regardless, we know what we need to know to guide public policy and personal behaviors: keep our distance and stay in place.

Colorado has done a fairly admirable job of affecting density and flow.  With less than a quarter the population of New York City or Texas, density is less of a problem in Colorado.  Looking at the state map of Covid-19, the axis of incidents follows density and flow, from Denver west along I-70 to several ski resorts, and north and south from Denver along I-25, a major commercial corridor and the unfortunate venue of a bridge tournament a few weeks ago in Colorado Springs that created a Covid-19 hotspot.  Colorado Governor Polis was absolutely right to shut down ski resorts on March 15^th; in hindsight, he should have done it sooner.  Eagle County, home to Vail and Beaver Creek ski resorts, is second only to Denver in Covid-19 cases.  Flow (of snowbound tourists) matters too.  Moving forward, notwithstanding damaging economic effects, or the prospect of a scientific and/or medical breakthrough, we must do everything we can to reduce both the density and flow of humans.

I understand we all want to get back to social interactions and freely going wherever we desire.  Lately, our president is making noise that he wants our wealth and his poll numbers back where they were in February, and is suggesting we will be able to return to our active selves by Easter, but doing so prior to seeing data that confirms viral transmission and death rates have both ebbed and are in retreat is a foolish violation of the physical realities that confront us.  Economic activity, which (at least as of today) requires both the density and flow of humans will increase both the velocity of money and the virus.  Releasing our bonds of probity would sacrifice any flattening of the curve we have thus far sacrificed for, and put us back where we were, on a steep ascent to death and further economic destruction.  If we want to get out of this sooner than later—if we desire the summer of 2020 to be similar to 2019—we must have the discipline to take our medicine, as distasteful and disruptive as it is.  Discipline will end this crisis; social, economic, and political greed may produce years of peril rather than months.

It’s going to get tougher rather than easier for the foreseeable future, but we must honor the challenge we face with both fortitude and compassion.