An unsuspected case of COVID-19 — hospitalized as the pandemic was beginning in the United States — exposed 43 healthcare personnel (HCP) and caused what are thought to be the first occupational infections with the virus, the Centers for Disease Control and Prevention (CDC) reported.1

On Feb. 26, the first U.S. case of community-acquired COVID-19 was confirmed in a patient at “hospital B” in Solano County, CA. Initially, the patient had been evaluated at a different facility, “hospital A,” the CDC reported.

“At that time, COVID-19 was not suspected, as the patient denied travel or contact with symptomatic persons,” the CDC noted. “During a four-day hospitalization, 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.”

Several days later, the patient tested positive for SARS-CoV-2, the virus that causes COVID-19.

“Among 121 hospital A HCP who were exposed to the patient, 43 (35.5%) developed symptoms during the 14 days after exposure and were tested for SARS-CoV-2,” the CDC noted. “Three had positive test results and were among the first known cases of probable occupational transmission of SARS-CoV-2 to HCP in the United States.”

Other healthcare workers could have been infected with the virus but were not picked up in the testing, the CDC acknowledged. Workers were tested through nasopharyngeal and oropharyngeal specimens, but serological testing was not performed. Likewise, additional infections might have occurred among asymptomatic-exposed HCP who were not tested.

“It is possible that additional infections may have occurred among the 40 symptomatic healthcare personnel who tested negative, due to potential limitations in test sensitivity and timing,” says lead author Amy Heinzerling, MD, an officer in the CDC Epidemic Intelligence Service. “It also is possible that their symptoms were caused by other respiratory infections or by noninfectious causes such as seasonal allergies. Most of these 40 healthcare personnel had mild symptoms, and none required hospitalization.”

The three infected staff members performed more physical examinations of the patient and had longer exposures during nebulizer treatments without wearing personal protective equipment (PPE).

“Because transmission-based precautions were not in use, no HCP wore PPE recommended for COVID-19 patient care during contact with the index patient,” the CDC concluded. “Healthcare facilities should emphasize early recognition and isolation of patients with possible COVID-19 and use of recommended PPE to minimize unprotected, high-risk HCP exposures and protect the healthcare workforce.”


  1. 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. MMWR Morb Mortal Wkly Rep 2020;69:472-476.