Since all we seem to hear about these days is COVID-19 I have tried to not write anything on the topic. However, the phrase “flattening the curve” keeps coming up and few people seem to comprehend what it means. I have a suspicion that most people have never actually considered what the graph they are referring to would look like or what it depicts, so let’s take a quick look and see if that clears up some confusion.
The first graph depicts the expected progression of the virus with no intervention. In this case, it spreads to the whole population quite quickly. Eventually, the size of the population limits any further spread, as most people have had it already.
In the second graph, the spreading of the virus is slowed down after the initial peak. However, social distancing does not completely prohibit the virus from spreading since it is done imperfectly and some people are still working. The lower-than-normal interaction among people keeps the number of infected people at any given time down.
In either case, the number of people that are expected to get infected and need medical assistance – the area under the curve – is the same. It is the blue area – the area under the curve but above hospital capacity – that we are concerned with. A certain amount of people will get infected and not make it, despite getting the medical attention they need. There is not much we can do about that. The deaths we are trying to avoid are the deaths in the blue zone, where people need attention but do not get it. In order to make this group as small as possible, we need to either increase the capacity (shifting the red line up) or keep the number of infected people down (flattening the curve).
Increasing the capacity sounds like a good idea, but it is tough in practice. Hospitals take time to build doctors and nurses take time to train, and making more equipment takes time too. Time we do not have available. In different circumstances, it might be possible to get doctors and surplus equipment from other places to temporarily increase the capacity and set them up in temporary hospitals – this would take relatively little time. Yet, as the rest of the world is in the same boat or anticipating that they will be, shortly, there is no surplus to borrow.
This leaves only the option of flattening the curve. As can be seen in the second graph above, the idea is to keep the number of infected people at any given time below hospital capacity. Done properly, people still get infected, but the ones who need medical treatment still have it available. It follows then, that once the social distancing regulations are made more lenient, we should still expect new cases. Hopefully just not enough to exceed the capacity line.
The strategy in Sweden – another popular topic – is based on the idea that the health care system will have the capacity to deal with the outbreak without slowing it down. Theoretically, no more deaths should result from this strategy, but the death toll early on will be higher due to the number of people infected. Their graph would look something like this:
Think about it as paying for something in installments. For the sake of ease, picture buying a car that costs $10,000. Most people do not have the capital available to pay the full amount upfront. Instead, they choose to pay monthly installments of $364 for 30 months. Essentially, this is what most countries are doing. They do not have the money (hospital capacity) to pay the full amount upfront, so they are prolonging the payment period and paying in smaller amounts – Sweden, having the available cash, is simply paying the full amount upfront. As most people know, these installment plans are not free though and you need to pay interest. The interest being paid for flattening the is the cost of shutting down large parts of the economy to facilitate social distancing to the maximal (practical) degree.
Ideally, we would all want to pay the full amount upfront and avoid the steep interest rate charged, but without the available resources, we are forced to pay in installments and eat the interest costs. We simply have no choice if we wish to avoid higher death rates.