Simulating an Epidemic: Using Data to Show How Diseases Like COVID-19 Spread

Dis­ease mod­el­ing as a sci­ence has come into its own late­ly, for heart­break­ing­ly obvi­ous rea­sons. What may not be so obvi­ous to those of us who aren’t sci­en­tists is just how crit­i­cal data can be in chang­ing the course of events in an out­break. Virus out­breaks may be “acts of God” or acts of unreg­u­lat­ed black mar­kets and agribusi­ness­es, but in either case, sta­tis­ti­cal mod­els can show, con­crete­ly, how col­lec­tive human activ­i­ty can save lives—and show what hap­pens when peo­ple don’t act togeth­er.

For exam­ple, epi­demi­ol­o­gists and bio­sta­tis­ti­cians have shown in detail how social dis­tanc­ing led to a “decline in the pro­por­tion of influen­za deaths,” one study con­cludes, dur­ing the 1918 flu pan­dem­ic. The same researchers also saw evi­dence in their mod­els that showed “pub­lic risk per­cep­tion could be low­ered” when these prac­tices worked effec­tive­ly, lead­ing peo­ple think they could resume busi­ness as usu­al. But “less social dis­tanc­ing could even­tu­al­ly induce anoth­er epi­dem­ic wave.”

To say that it’s a chal­lenge to stay inside and wait out COVID-19 indef­i­nite­ly may be a gross under­state­ment, but hun­ker­ing down may save our lives. No one can say what will hap­pen, but as for how and why it hap­pens, well, “that is math, not prophe­cy,” writes Har­ry Stevens at The Wash­ing­ton Post. “The virus can be slowed,” if peo­ple con­tin­ue “avoid­ing pub­lic spaces and gen­er­al­ly lim­it­ing their move­ment.” Let’s take a look at how with the mod­el above. We must note that the video above does not mod­el COVID-19 specif­i­cal­ly, but a offers a detailed look at how a hypo­thet­i­cal epi­dem­ic spreads.

Cre­at­ed by YouTu­ber 3Blue1Brown, the mod­el­ing in the top video draws from a vari­ety of sources, includ­ing Stevens’ inter­ac­tive mod­els of a hypo­thet­i­cal dis­ease he calls “simuli­tis.” Anoth­er sim­u­la­tor whose work con­tributed to the video, Kevin Sim­ler, has also explained the spread of dis­ease with inter­ac­tive mod­els that enable us to visu­al­ize dif­fi­cult-to-grasp epi­demi­o­log­i­cal con­cepts, since “expo­nen­tial growth is real­ly, real­ly hard for our human brains to under­stand” in the abstract, says YouTube physics explain­er Minute Physics in the short, ani­mat­ed video above.

Deaths mul­ti­ply faster than the media can report, and what­ev­er totals we come across are hope­less­ly out­dat­ed by the time we read them, an emo­tion­al and intel­lec­tu­al bar­rage. So how can we know if we’re “win­ning or los­ing” (to use the not-par­tic­u­lar­ly-help­ful war metaphor) the COVID-19 fight? Here too, the cur­rent data on its pre­vi­ous progress in oth­er coun­tries can help plot the course of the dis­ease in the U.S. and else­where, and allow sci­en­tists and pol­i­cy-mak­ers to make rea­son­able infer­ences about how to stop expo­nen­tial growth.

But none of these mod­els show the kind of gran­u­lar­i­ty that doc­tors, nurs­es, and pub­lic health pro­fes­sion­als must deal with in a real pan­dem­ic. “Simuli­tis is not covid-19, and these sim­u­la­tions vast­ly over­sim­pli­fy the com­plex­i­ty of real life,” Stevens admits. Super-com­pli­cat­ing risk fac­tors like age, race, dis­abil­i­ty, and access to insur­ance and resources aren’t rep­re­sent­ed here. And there may be no way to mod­el what­ev­er the gov­ern­ment is doing.

But the data mod­els show us what has worked and what has­n’t, both in the past and in the recent present, and they have become very acces­si­ble thanks to the inter­net (and open source jour­nals on plat­forms like PLOS). For a longer, in-depth expla­na­tion of the cur­rent pan­demic’s expo­nen­tial spread, see the lec­ture by epi­demi­ol­o­gist Nicholas Jew­ell above from the Math­e­mat­i­cal Sci­ences Research Insti­tute (MSRI).

It may not sway peo­ple who active­ly ignore math, but dis­ease mod­el­ing can guide the mere­ly unin­formed to a much bet­ter under­stand­ing of what’s hap­pen­ing, and bet­ter deci­sions about how to respond under the cir­cum­stances.

Relat­ed Con­tent:  

Spring Break vs. COVID-19: Map­ping the Real Impact of Ignor­ing Social Dis­tanc­ing

Watch “Coro­n­avirus Out­break: What You Need to Know,” and the 24-Lec­ture Course “An Intro­duc­tion to Infec­tious Dis­eases,” Both Free from The Great Cours­es

The His­to­ry of the Plague: Every Major Epi­dem­ic in an Ani­mat­ed Map

Josh Jones is a writer and musi­cian based in Durham, NC. Fol­low him at @jdmagness