Covid-19 / Resources

COVID-19 Prevalence Calculator

Rendering of the 2019-nCoV virion. Dan Higgins, MAM/CDC/REUTERS

Key Premise

Since case counts are highly related to the amount of testing done, deaths (which tend to be more easily detected) can be used to estimate the total number of cases.

Other assumptions

  1. The number of COVID-19 related deaths is easier to ascertain that the number of cases
  2. The number of true COVID-19 infections includes asymptomatic cases, presymptomatic cases, symptomatic cases, deaths and recovered patients
  3. The Infection Fatality Rate or Ratio (IFR) is the number of deaths over the total number of infections, and is influenced by many factors including age distribution of a population and case management
  4. There is a lag of approximately 2 weeks (or 14 days) on average between illness onset and death, see: Case-Fatality Risk Estimates for COVID-19 Calculated by Using a Lag Time for Fatality (CDC)
  5. Cases in the past 14 days will have a similar case fatality rate as those prior to 14 days ago

Caveats/Disclaimer:

This calculator provides a rough estimate and does not consider all of the important factors that impact cases and deaths. It will be inaccurate if deaths are highly clustered in a population (heterogenous), so that the number of deaths would not necessarily imply a certain amount of cases in the population.

  • For instance in a community where the majority of deaths occur in a congregate facility (e.g. nursing home or prison), transmission may be restricted to those areas leading to higher deaths relative to the number of cases
  • In this case the calculator will overestimate the number of cases

It will be inaccurate if high deaths rates were a result of intense transmission that overwhelmed health care system capacity leading to suboptimal case management. In this case the calculator will overestimate the number of case.

How to use the calculator

In order to use the calculator you need the following information as inputs:

Once you have this information, enter it into the Inputs area

The calculator estimates an age-adjusted infection fatality rate (IFR) which is the percent of total infections that results in death. For more information on IFR visit CEBM.net . If you want to enter your own IFR, you can do it in the box (otherwise it will use what is calculated)

After entering the information, you will get the result. The boxes below will be populated with estimates based on your inputs:

Examples from New York City, the United States, Africa and the World are provided for reference (as of information on May 5, 2020)