How Many People Are Tested for COVID-19 Are Actually Infected?

April 15, 2020

From Ahvie Herskowitz, MD

While infection rates are probably underestimates (improperly performed and/or timed tests will be falsely negative), looking at how many persons tested for COVID19 actually tested positive yields very useful information.

In the USA, where we test primarily only symptomatic persons presenting to the hospital, we find that 20% of tested persons are positive for COVID19.

In Korea, with more widespread population testing, we find that 2% of tested persons are positive.

Other countries offer a wide variance, but nowhere are the majority of symptomatic persons testing positive. Russia is an outlier with 1.5 million tests and only about 25,000 positive cases. In other words, only 1 in 750 persons tested actually had the virus.

We won’t know the prevalence of COVID19 until widespread testing is implemented (very unlikely in the near future) OR a random sampling of different regions in the USA are compared (ie New York City, Chicago, New Orleans vs San Francisco or Los Angeles vs rural areas).

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About Ahvie Herskowitz, MD

Dr. Herskowitz’s extensive training includes a medical degree from The Albert Einstein College of Medicine, residencies in Anatomic Pathology and Internal Medicine, and Fellowship training in Cardiology at The Johns Hopkins Medical Center. During his 12 years at Johns Hopkins, he became Associate Professor of Medicine and Immunology and Molecular Microbiology and led a research team in the study of molecular and immunological mechanisms of inflammation, autoimmunity, ischemia, heart transplantation rejection and congestive heart failure.

Dr. Herskowitz’s latest academic appointment was as Clinical Professor of Medicine at UC San Francisco. To learn more about Dr. Herskowitz, you can read it bio here.


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