OK, before someone gets upset I’m not taking the current crisis seriously, don’t misunderstand: this is a serious situation. But there is no cause to lose our sense of humor or be grim. Yes, we must take action, but no, it’s not the end of the world (unless you’re a nurse or doctor, then it might feel like it for a couple of weeks). I’ll crunch the numbers downthread and it’s not as bad as you might think if you keep perspective. But do not doubt the sad fact that the US health care system can’t really keep up with a normal flu season; there is no way it can handle a rapid influx of respiratory patients. That is why COVID19 is so dangerous, and why everyone needs to take it seriously, following the CDC guidelines, limit interactions outside your immediate household (aka social distancing), keep strict hygiene protocols, and otherwise doing everything you can to try to slow down the rate of spread. It’s more than likely not about you. It’s about that 1% of so of the population who will get very sick, and may not get enough care because the system will be overloaded.
Here’s the latest analysis. First, please, please, please, stop obsessing on every blip in the numbers! They are not “skyrocketing” or whatever inflammatory phrase the media is using at the moment. Second, the absolute numbers don’t matter. Yes, each and every one is a life, and a tragedy. But what matters in terms of risk is the denominator: how many people are getting sick and passing away in terms of what size group? Losing 100 people in Chatham County (pop about 290,000) is very different from losing 100 people in New York City (pop 8.6 million). Don’t compare them. It’s mortality per unit population that matters – and how fast that mortality happens. Please stop feeding the beast by quoting and hyping how many deaths per day without context. It’s not helpful, and causing people far more stress than is appropriate.
Time for some math: deaths from the virus are progressing along what is known as a logistic function. This type of function was originally developed for use in population growth, but has found it’s way in to many other fields. In biology, this is sometimes called a carrying capacity curve. We are entering the scary part of that curve. Here’s what the curve looks like with data for several areas as of 24 March 2020. The black line is a theoretical curve that represents an estimate of how things might progress. The grey line is for comparison, the 2017 H3N2 flu progression speeded up by a factor of 5. The dots represent actual data as of the totals for yesterday as reported this morning. Click to embiggen …
Of these, China (grey +) and Iran (blue o) look weird. I suspect those numbers are “munged.” But Spain (red dots) and Italy (green dots), which are the farthest along of societies that might resemble the US, seem ok. (South Korea is even further down the curve, but they took very early intervention, and have more hospital surge capacity than the US, so may not be a good analog). New York is the cyan triangles that are hard to see because it’s just starting to creep along the curve – about day 25 or so. The next 20 days will be very scary – you can see that is the steepest part of the curve, and people will talk about doubling times, and extrapolation the daily rates far beyond the point where they will start to settle down.
Where will it end? The latest projections are that the US will see between 50 and 90 thousand deaths. (2017 saw 61 thousand H3N2 influenza deaths – but over 6 months, not 6 weeks!). New York will likely see upwards of 5 thousand (currently 200 or so). Smaller communities will also see a rapid rise in deaths that, without context, will seem terrifying. Expect the health care system to be in crisis, and please do what you can to support the medical community. This will be horrific for them. Chatham County, Georgia hospitals, which serve about 400,000 people, will likely see nearly 1,000 respiratory cases, of which 100 may die, all in the next three weeks. But again, by the end of April, most parts of the country should be at the upper end of the curve, with the deaths per day decreasing.
How soon will we know if that is our future, or something worse? Italy should be at near their peak. I expect that by early next week we will see a downward trend in their numbers, followed by Spain 4-5 days later. If by the 1st of April Italy is still recording 700 or more per day, that will be a source of concern. Will update the graph this weekend … meanwhile, don’t hoard TP like this guy.