A Statistical Model for Flattening the Curve

The folks at SURF Stanford Medicine have made available a COVID-19 calculator that allows healthcare providers and policy makers to estimate ICU and acute care bed demand for COVID-19 patients. Why is this important? I’ve previously addressed social distancing which is one of our most effective methods to flatten the curve at present, given that a vaccine is still under development and we still have a huge shortfall in diagnostic testing capacity. Flattening the curve allows our health systems to “buy time” and avoid over-saturating our ability to deliver care to patients who need it. Exceeding our health system capacity will mean that doctors will be forced to ration care (i.e., treat the ones who are most likely to survive and let others potentially die).

The calculator includes a variety of inputs that enable users to more accurate forecast the impact to their local area hospitals. For example, one can input the cumulative confirmed cases as of today, and this data is available from a variety of public sources. Another input is the doubling time which is the number of days it takes, at the current trajectory, for the number of cases (or hospitalizations, if you choose to use that as the basis for your model) to double. There are also variables for symptomatic cases per confirmed case and number of days to model ahead. These all impact the steepness of the curve.

I think that the most interesting aspect of this calculator is the ability to simulate the impact of social distancing interventions. The calculator provides the ability to enter new doubling times on 3 different days, and each new doubling time is modeled into the shape of the curve.

This model reflects a population that does a poor job of social distancing.

This model reflects a population that practices effective social distancing.

While this calculator is intended for use by healthcare providers and policy makers, I think it would also be useful for the general public to use this tool to visualize the potential impact of social distancing on our healthcare system. If we can all shelter at home, cover our coughs and sneezes, disinfect surfaces as needed, and take all the precautions, we can reduce transmission of COVID-19. Reduction of transmission will result in higher doubling times, and the general public can see the impact of social distancing on flattening these curves.