It is possible 1 million healthcare workers have been infected with COVID-19, as public health officials report there likely are 10 unknown cases for every one that is documented.

As of July 1, the Centers for Disease Control and Prevention (CDC) reported 88,763 COVID-19 infections in healthcare workers with 483 deaths.1 However, the precise count likely is much worse, as the CDC data came from limited reports. These limitations include the many asymptomatic cases or those with symptoms who were never tested.

“[That is] one of the realities because this virus causes so much asymptomatic infection,” CDC Director Robert Redfield, MD, said at a recent press conference. “Again, we don’t know the exact number. There are ranges between 20%, as high as 80% in different groups. The traditional approach of looking for symptomatic illness and diagnosing it obviously underestimated the total amount of infections.”

The CDC is using more serology tests and the new assays for antibodies, Redfield added. These diagnostics clearly suggest the numbers are much higher than the official tallies, perhaps by a range of multiples from 5 to 1, to 12 to 1, he noted.

“I think a good rough estimate right now is 10 to 1,” Redfield said. “I wanted to highlight that because at the beginning, we were seeing diagnosis in cases of individuals who presented in hospitals, emergency rooms, and nursing homes. We were selecting for symptomatic or higher-risk groups. There wasn’t a lot of testing that was done of younger-age, asymptomatic individuals.”

That means roughly 90% of the outbreak has been the bottom of the iceberg for both healthcare workers and the general public, at least for March through May. “We are continuing to try to enhance surveillance systems for individuals who are asymptomatic to be able to start detecting that asymptomatic infection more in real time,” he says.

Redfield did not try to extrapolate the ratio to patient and healthcare worker deaths, but the CDC concedes the latter are based on partial data that underestimates the total.

Of the 88,763 cases in healthcare workers, death status was only available for 58,067, the CDC notes. Applying the tenfold formula to the national case count as of June 25 reveals a staggering 24 million cases.


  1. Centers for Disease Control and Prevention. Coronavirus disease 2019 (COVID-19): Cases in the U.S., July 1, 2020.