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Transmission of COVID-19 to Health Care Personnel During Exposures to a Hospitalized Patient — Solano County, California, February 2020

Our take —

This small study provided limited new information given our current state of knowledge. It is clear that additional precautions (wearing gowns, N95 masks, eye protection, and using air-purifying respirators) are needed to prevent health care workers from acquiring COVID-19 from patients.

Study design

Case Series

Study population and setting

The paper describes the symptoms, COVID-19 status, and occupational exposure of 121 health care personnel at a hospital in Solano County, California after treating a patient who later tested positive for COVID-19. At the time of exposure, the patient’s COVID-19 status was not known or suspected, so personal protective equipment such as eye protection, powered air-purifying respirators, N95 respirators, and gowns were not used during aerosol-generating procedures (e.g., nebulizer treatments). The patient spent a total of four days in the hospital between February 15 and February 19, 2020 before being transferred to a second hospital, where COVID-19 was diagnosed via PCR.

Summary of Main Findings

Out of the 121 health care workers who were at risk of acquiring COVID-19 from the patient, 43 developed symptoms (fever, cough, shortness of breath, and/or sore throat) and were tested. Of those tested, three tested positive. Of the three who tested positive, all had prolonged close contact with the patient.

Study Strengths

The study attempted to document differences in occupational exposure to COVID-19 based on procedure type and duration of exposure.


The small sample size (n=121) limits the conclusions that can be drawn from this study and expected to apply elsewhere. Making multiple comparisons between those with symptoms who tested negative (n=34) and those who tested positive (n=3) — when both had such small sample sizes — increases the probability of finding coincidental, untrue differences. Given our current understanding of the high prevalence of asymptomatic COVID-19, it would have been useful to test all 121 health care workers that were exposed instead of just those who developed symptoms. The paper also did not describe which test was used, which is an important detail, as the sensitivity and specificity vary by test type. It is also conceivable, if unlikely, that some transmission was between health workers rather than from the patient. Finally, all exposures were self-reported via recall, and as such, some health workers may not have accurately remembered all of their exposures.

Value added

Given what we know now, this study has limited added value. The small sample size (only 3 tested positive) undermines the validity of any observed associations between particular aerosol-generating procedures (e.g. nebulizer procedures) and positive cases.

This review was posted on: 4 July 2020