Thursday, May 7, 2020

Measuring COVID-19 at Two Levels

Environmental & Science Education
Nature of Science
History of Science
Edward Hessler

You may have seen the simulation of how a fake disease spreads in a community. The disease was known as "simulitis" and was published in the COVID-19 series of the Washington Post. The uninfected people were represented by gray dots and the infected people by red dots. When red contacted gray, those healthy persons became sick.

I didn't spend much time thinking about it but did wonder about the contact--cough, touch, its length and whether the infected people were symptomatic or asymptomatic. The game may suggest that simple--digital--contact is sufficient, at least it appears digital. Then I left left the page.
In a recent issue of The New Yorker, Siddhartha Mukerjee*, now a cancer oncologist, but who as a graduate student was trained in viral immunology, brought a much wider roving curiosity and background to the gray-dot-red-dot game than me. 
He writes, "The doctor and medical researcher in me...wanted to know what was going on within the dots. How much virus was in that red dot? How fast was it replicating in this dot? How was the exposure--the 'touch time'--relate to the chance of transmission? How long did a red dot remain red--that is, how did and individual's infectiousness change over time? And what was the severity of disease in each case?
Most, if not all, of my attention has been to the pandemic as an epidemiological issue--at the level of populations; not at the individual level. There are three questions, Mukerjee says "deserve particular attention." 
--"What can we learn about the 'dose-response curve' for the initial infection," i.e. quantifying risk as the individuals are exposed to higher viral levels?
--"Is there a relationship between that initial 'dose' of virus and the severity of the disease," are people sicker when exposed to higher viral exposure?
--"Are there quantitative measures of how the virus behaves in infected patients (e.g., the peak of your body's viral load, the patterns of its rise and fall) that predict the severity of their illness and how infectious they are to others."
Mukerjee explores these questions in his essay. Some of the experiments are downright ingenious and revealing. He spoke with viral researcher Rik de Swart (Erasmus University, Rotterdam who noted while emphasizing that meales and COVID-19 are two very different diseases, that in "'measles there are several clear indictns that the severity of illness relates to the dose of exposure. And it makes immunological sense, because the interaction between the virus and the immune system is a race in time."
Measurement of viral loads is very difficult, e.g., oral swabs are influenced by how they are taken but work reported by Joshua Schiffer, Fred Hutchinson Center, has reported "that more stringent nasal-swabbing methods (which sounds it might be nauseous) have yielded consistent, reliable viral load-counts, and that these loads have tracked well with disease symptoms and progression"
In clinical oncology, Mukerjee emphasizes "measurement and enumeration are the mainstays of" medical practice: "the size of a tumor, the number of metastases, the exact shrinkage of a malignant mass after chemotherapy and the stratification of response (categorizing patients according to their response to treatment)". These allow Mukerjee "to describe risk, explain how a remission is measured, and carefully devise a clinical plan"--all in about 30 minutes.
COVID-19 is different: it "goes hand in hand with panic." Measurements of the kind Mukerjee describes will in the end help medical professionals make better use of resources"--always scarce--and treat patients better.
So we must be able to detect the path of a virus at the population level as well as "its course within a single patient. The one becomes he many. Count both; both count." 
In his essay, Mukerjee elaborates on these points and also describes the history of inoculations for smallpox in India, noting the progress made along the way. You will be surprised, I think, by the ability of those inoculating others to precisely estimate the proper dose. Please read it. 
*Dr. Mukerjee is the author of several books. One of them was the Pulitzer Priize winning "The Emperor of All Maladies: A Biography of Cancer." 

Amazon lists and briefly describes his books

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