Fully 40% of healthcare workers who test positive for COVID-19 show no symptoms, and more than half of those who test positive are nurses.

That’s according to an analysis of up to 97 COVID-19 studies by investigators from Switzerland and Colombia. Some of the findings are derived from pooled research including more than 230,000 healthcare workers across 24 countries. From these data, the researchers were able to estimate the prevalence of infections at 7% to 11% in screened workers, based on which tests were used for diagnosis. 

Nurses tested positive for the virus at a rate of 58%, followed by physicians (25%) and other healthcare workers (23%). About one in 20 COVID-19-positive workers went on to develop severe clinical complications, and 0.5% subsequently died.

In addition, the choice to screen workers based only on symptoms of fever, cough, shortness of breath and sore throat may have missed 17% of early illnesses, the authors estimated. “Loss of taste and smell, muscle pain, and fever were identified as the only symptoms significantly associated with SARS-CoV-2 positivity among healthcare workers,” explained Taulant Muka, M.D., Ph.D., of the University Of Bern, Switzerland.

Based on these findings, the authors recommend standard universal screening for all exposed workers, regardless of symptoms. In addition, “it is clear that providing healthcare workers with adequate personal protective equipment and training is essential,” they said.

The study was published in the American Journal of Epidemiology.