Epidemics 101

So much of what Twitter “experts” say about reopening the country is wrong, misleading or irrelevant.  What most of them are missing is a basic understanding of the nature of an epidemic such as Covid-19.  In order to address this problem, I’ve created a little chart to show how an uncontrolled epidemic behaves.  

The earliest known case of Covid-19 goes back to November, 2019, so I start there.  I assume that an infected person spreads the disease to two others.  I also assume that 1 out of 6 infected is symptomatic enough to seek care and is tested positive, and that the infected mortality rate (IFR) is .007.  These numbers seem to be within the range of estimates for Covid-19, and they suffice for illustration purposes.  It is not intended to be accurate historically, or a prediction of anything.  It is merely an example of how an uncontrolled epidemic spreads.

For what it’s worth, as of this writing (May 8, 2020), there are just over 4 million confirmed cases and 276 thousand deaths.  

The most important number in terms of containment is how many people catch the disease from an infected individual.  The only guaranteed way to prevent further infection is to make sure that an infected person does not come into contact with somebody who has not been infected.  The problem is that not everyone who is infected is symptomatic, and the virus can spread before the symptoms manifest themselves.  Therefore, we don’t know who to keep isolated, which is why there is social distancing and stay at home policies.  

In my chart, I assumed that an infected person would spread the infection to two more.  In reality, an infected person who is not symptomatic, or who is presymptomatic, would likely spread the infection to 3 or more individuals.  This is easy to understand, because my chart is based on unrestrained spread, and there have been worldwide efforts to contain the virus for months.  It is much more likely that the initial spread was faster than my chart shows and slowed as a result of the containment measures taken.

Now, just imagine what happens when those restraints are removed.  Of course, individuals who have been diagnosed will be isolated, but we know that there are many more undiagnosed cases.  A recent study in New York estimated that there were about six undiagnosed cases for each confirmed case.  That means that there are likely several million individuals who are currently infected, and if social distancing rules were immediately lifted, there would be an explosion of new cases as those individuals start interacting with others.

One argument you are likely to encounter is that the only people who die from the coronavirus are people in nursing homes or those who are already sick.  If you’re not at risk, the argument goes, the worst you’ll experience is something comparable to the flu.  There is a bootstrapping component of this argument, because they define a healthy person as one who did not suffer severe symptoms from the coronavirus.  Over 100 New York City transit workers have died of the virus, and as far as I know, very few of them lived in nursing homes.  Another interesting thing is that there is a significant overlap between those who are willing to let nursing home residents die en masse and right to lifers.  Go figure.

If we are going to dismiss the lives of nursing home residents as worthless, we might as well be up front about it and euthanize them.  After all, they are a drag on the economy, but in fairness, we should have a bailout for the For Profit Nursing Home Operators who will lose their customer base.