How many people are walking around infected with Covid-19?

Finally, some C-19 “prevalence” estimates…

Loyal readers know that I’ve been frustrated by the lack of practical, personally-relevant data that the public health “experts” have been gathering, analyzing and disseminating.

For example, I’d like to know how likely I am to bump into a person who is infected with C-19 if I leave my house.

Reasonable question, right?

In infectious disease speak, that number is called the “prevalence rate” … the percentage of people in an area who are infectious-likely at a specific point in time.

Current testing procedures don’t answer the question (see: Why is COVID testing still so haphazard?) … so, the “experts” fixate on metrics that are muddled and potentially misleading (see: Birx: “Key metric that I watch is the positivity rate”).

Finally, I’ve stumbled on some “machine learning” analyses that take a stab at answering my question: What’s the Covid prevalence rate?


OK, let’s get to work…


First, an important disclaimer:

  • Most of today’s data is drawn from a site called that relies on an “intuitive model that builds machine learning techniques on top of a classic infectious disease model.”
  • The model and site are the product of the University of Washington’s oft-maligned Institute for Health Metrics & Evaluation (IHME) which generated many of the early inaccurate Covid forecasts (see: What you need to know about the IHME Model)
  • That said, I think that IHME is a credible source since its models are logical and very much data-driven.  And, IHME is very transparent. It even provides details of its approach and even links to analyses that are critical of it’s work.
  • My conclusion: IHME’s early forecast errors were mostly a function of the sparse data set that they had to work with early-on.  The data set is still problematic … but it’s getting better, so IHME has more to to work with.


Top-line numbers…

Note: All numbers should be considered approximate since they are estimates, not actuals … and, I’ve done some heavy rounding to make the numbers easier to internalize.

Primary source: IHME Covid Projections

OK, so what do the numbers say?

Already infected: IHME estimates that 40 million Americans have already been infected with the coronavirus … that’s about 12.5% of the total population (1 in every 8 people) …  or, about 17% of the 19 & over adult population (1 in every 6 adults).

Confirmed cases: To date, there have been about 5 million confirmed cases … that’s about 1.5% of the total population (2% of the adult population) … and, the number of confirmed cases is about 12.5% of total infections to date (based on the IHME estimate of those already infected) … said differently, only 1 in every 8 infections have been confirmed by Covid testing.

New infections & confirmations: IHME estimates that there are currently 400,000 new infections each day … of which, about 60,000 (15%) are confirmed via testing.   (Note: The 15% current rate is higher than the 12.5% total rate since testing has been ramped up).


And, for the critical number …

Prevalence: IHME estimates that there are currently 6 million “active infections” … that’s a prevalence rate of 1.85% of the total population (1 in every 54 people) … or, 2.5% of over-19 adults (about 1 in every 40 adults).


Note: The “positivity rate” that Dr. Birx watches — the percentage of tests that return a positive diagnosis — is running about 8%.  Why? Because the vast majority of people getting tested have symptoms or have been exposed to someone who has tested positive.  They don’t reflect the profile of the overall population.


What are my local odds?

OK, now we’re getting someplace … a national prevalence rate of 1.85%.

But, what really matters (to me) is the Covid prevalence in my local area.

IHME takes a stab at localizing the estimates.

For example, IHME estimates that my home state (Maryland) has a prevalence rate of 1.55% that is:

  • Lower than the 1.85 national average
  • Lower than the current hot spot states: FL 4.47%, TX 3.91%, CA 2.14%
  • Higher than “cool” states, e.g. SD, ND, MT, OH that are running between 1.0% and 1.5%

Of course, I’d like a more localized number, e.g. the covid prevalence in the Annapolis area.

But, finally. I think I’ve got a ballpark number to work with.


Now, if only public health officials would use the testing apparatus to gather, analyze and report Covid data that helps us make decisions re: how to live our lives.

I’m not holding my breath…

2 Responses to “How many people are walking around infected with Covid-19?”

  1. Mike Gehringer Says:

    By my reading, PA is at 0.51% prevalence rate… and NJ, shockingly, is at 0.37%. Is that right?

  2. Ohio Gov. DeWine tests negative … after testing positive. | The Homa Files Says:

    […] See How many people are walking around infected with Covid-19? […]

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: