Among 121 healthcare personnel (HCP) exposed to a patient with unrecognized coronavirus disease 2019 (COVID-19), 43 became symptomatic and 3 tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). These 3 HCP all had contact with the patient without personal protective equipment and exposure while performing physical examinations or during nebulizer treatments were more common. These findings were published in Morbidity and Mortality Weekly Report.

The first confirmed US case of community-acquired COVID-19 was confirmed February 26, 2020 in Solano County, California. This patient was initially evaluated in hospital on February 15, but COVID-19 was not suspected because the patient denied any travel or contact with symptomatic persons. During this 4-day stay, the patient was managed with standard precautions and underwent multiple aerosol-generating procedures, including nebulizer treatments, bilevel positive airway pressure ventilation, endotracheal intubation, and bronchoscopy. The patient was subsequently transferred to a second hospital and confirmed positive via reverse-transcriptase polymerase chain reaction testing for SARS-CoV-2.

A total of 121 HCP were exposed to the patient at the first facility. Of these 43 became symptomatic during the 14 days post exposure and were tested; 3 of them received a positive diagnosis for SARS-CoV-2. The median time from last exposure to specimen collection was 10 days. These 3 individuals comprise the earliest cases of COVID-19 among HCPs. Because little is known about the specific risk factors for transmission in healthcare settings, standardized interviews were conducted with 37 of the HCP tested.

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Seventeen (46%) of 37 interviewed HCP reported exposure to the patient during at least 1 aerosol-generating procedure. HCP who were present for or assisting with nebulizer treatments more commonly developed COVID-19 (67%) compared with those who did not (9%) (P = .04); being present for or assisting with BiPAP was also more common among HCP who developed COVID-19.

According to investigators, HCP who developed COVID-19 had longer durations of exposure (120 minutes vs 25 minutes; P = .06) and were more commonly exposed during nebulizer treatments and bilevel positive airway pressure ventilation. HCP at high or medium risk were furloughed and actively monitored; those at low risk were asked to self-monitor for symptoms for 14 days from their last exposure.

“These findings underscore the heightened COVID-19 transmission risk associated with prolonged, unprotected patient contact and the importance of ensuring that HCP exposed to patients with confirmed or suspected COVID-19 are protected.”

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The findings were subject to several limitations, the first being that exposures were self-reported and may suffer from recall bias. Second, there were a low number of cases, which limited the ability to detect statistically significant differences and does not allow for multivariable analyses adjusting for potential confounders. Third, serologic testing of HCP was not performed and additional infections might have occurred in asymptomatic exposed HCP who were not tested.

The Centers for Disease Control and Prevention recommends the use of N95 or higher-level respirators and airborne infection isolation rooms when performing aerosol generating procedures for patients with suspected or confirmed COVID-19. For care that includes aerosol-generating procedures, the use of respirators where available is recommended. Investigators concluded that, “to protect HCP caring for patients with suspected or confirmed COVID-19, health care facilities should continue to follow CDC, state, and local infection control and PPE guidance.” Early recognition and isolation, including source control, for possible infections can also help to minimize unprotected and high-risk HCP exposures.


Heinzerling A, Stuckey MJ, Scheuer T, et al. Transmission of COVID-19 to health care personnel during exposures to a hospitalized patient – Solano County, California, February 2020. Morb Mortal Wkly Rep. 2020;69:472-476.

This article originally appeared on Endocrinology Advisor