Wait - why is Jason talking about COVID-19? And why are these written like FaceBook posts? There’s a longer explanation here but the short version is that my day job for the past 15 years has been developing models of human health effects and medical response for chemical injuries and biological illnesses, including pandemics. I’ve been making these posts on FaceBook and I was asked to put them in a more shareable manner. I’m linking to the posts on the explanation page. These are the original, unedited posts. I’ll continue until I run out of things to say.
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Originally posted here on 3/22/2020.
Yet another COVID-19 tangential post, this one about the time course of illness (how long it takes for a disease to run through the body). Or, more specifically, how do we model the progression of signs and symptoms of illness in a single person?
[Note: this morning I realized that one of my papers on consequence management and patient care in mass-casualty events from 2015 is approved for public distribution. That paper has a pretty good timeline of the projects I was the Principal Investigator on since 2005, which gives a bit more context on my experience with this topic. It’s available here: https://pdfs.semanticscholar.org/…/cfcb800dea2134472f40e2a0…]
I haven’t studied this in COVID-19 yet. I hope to. But as a general practice, when modeling the time course of illness in a person it is best to start with a model of how the disease would progress in the absence of any treatment by defining
1) the onset time (the time at which symptoms begin to manifest)
2) the time-dependent severity (progression of disease severity as a function of time; how long it takes for symptoms to worsen) whether or not the person will die without treatment
3) the time-to-death if the person dies without treatment
4) the time to recovery if the person doesn’t die
These components are generally modeled as statistical distributions if the data can support it (as in you’ll have an average symptom onset time and then a range of onset times around that average - for example, COVID-19 could have a symptom onset of 3-14 days with an average of 5 days).
The trickiest part with modeling the time course of illness is the progression of disease severity as a function of time. From what I’ve seen from reports on COVID-19, fever seems to be correlated to disease severity - if you’re going to have a severe infection, it will come with a high fever. In that regard, I would probably model the severity of the disease as a function of fever.
This is not without precedent, and is something that my group has done before. We most recently developed a fever model for influenza, but the framework and pedigree of that model was based on data from something called Operation Whitecoat. Here’s something that sounds like fiction but it is completely true: Operation Whitecoat was a decades-long program from back when the US had an bio weapons program. In this program, conscientious objectors volunteered to be exposed to a handful of weaponized biological agents in order to test the efficacy of vaccines and to study their time course of illness. During these studies in which literally hundreds of individuals were subject to very high exposures, meticulous notes were taken on each patient including their symptoms, anecdotal notes, and vital signs - including body temperature. A couple of notes - this was way before I was born (the program ended in 1973), no one died during the study, and one of the Whitecoats actually maintains a website about his experiences: https://usarmywhitecoat.com/
Ok, now go ahead and Google it, and then come back.
Anyway, because of the Whitecoats we know quite a bit about disease severity and human performance as it relates to body temperature (among other symptoms). I would probably apply some of that data to disease severity of COVID-19. At this point we’d have a model of onset time and disease severity, not a model of lethality. There has been some data to estimate lethality with treatment and without treatment, possibly by using the age-dependent death rates coming out of South Korea and Italy, respectively.
You put all of that together and you get the most important data points you would need for medical modeling: 1) how MUCH STUFF you need and 2) WHEN you need it by. Beds, ventilators, specialists, treatments. You can get estimates of how much you need and when you need it by looking at the progression of illness in a collection of individuals.
Anyway, that’s all for today. It’s once again sunny in Arlington, VA. I plan on doing some yard work and some house work today. Yesterday we went for a nice, long hike with two dogs, a canteen of water, and a canteen of wine. Hope you all are self-quarantining, taking time to look away from the news, and helping your community. On my end, since we’re not going out at all, I’ve donated money to Arlington Food Assistance Center (https://afac.org/) and Doorways for Women and Families (https://www.doorwaysva.org/), two charities that are having very specific challenges resulting from COVID-19. Please check them out, or look for charities in your communities.
Stay safe. Call someone you haven’t spoken to in a while. Love you all, fam and friends and everyone else, really.
You can read more of my COVID-19 tangential posts here: https://www.jasonrodriguez.com/…/covid-19-a-hopefully-brief…. Once again, this post and all posts going forward, is turned into readable English by my editor, Liz Laribee.
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These are my opinions and thoughts and analyses - I am not representing any government agency or my company. More disclaimers on the main page.