Exposure Types and Transmission of COVID-19 in Health Care Settings


The study examined the effects of unprotected, prolonged patient contact, along with certain exposures, on the risk of health care providers becoming infected with COVID-19.


Health care providers (HCPs) are at an increased risk of acquiring coronavirus disease 2019 (COVID-19) as a result of exposures to patients with the virus. 

A new study published in the CDC’s Morbidity and Mortality Weekly Report examines the effects of unprotected, prolonged patient contact, along with certain exposures, on the risk of HCPs becoming infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

“This investigation presented a unique opportunity to analyze exposures associated with COVID-19 transmission in a health care setting without recognized community exposures,” the study authors wrote. “Describing exposures among HCP who did and did not develop COVID-19 can inform guidance on how to best protect HCP.”

For the analysis, standardized interviews were conducted with 37 HCPs who were tested for SARS-CoV-2 from the hospital (hospital A) where the patient who became the first US confirmed case of community-acquired COVID-19 was initially evaluated. Three of the HCPs interviewed tested positive.

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According to the findings, performing physical examinations and exposure to the patient during nebulizer treatments were more common among HCP with laboratory-confirmed COVID-19 than among those without the virus. Being present for or assisting with nebulizer treatments was more common among those who developed COVID-19 (67%) than among those who did not (9%) (p=0.04), the study found. 

HCPs with COVID-19 also had exposures of longer duration to the patient. The median estimated duration of overall exposure to the patient was higher among HCPs with COVID-19 (120 minutes) compared with those without the virus (25 minutes) (p=0.06). The median duration of exposure during aerosol-generating procedures (AGPs) was higher among HCP with COVID-19 (95 minutes) than among those without COVID-19 (0 minutes) (p=0.13). Performing physical examinations was also moer common among HCP with COVID-19. 

Additionally, because transmission-based precautions were not in place yet, no HCP wore personal protective equipment (PPE) at the time.

CDC recommends use of N95 or higher-level respirators and airborne infection isolation rooms when performing AGPs for patients with suspected or confirmed COVID-19, according to the authors. For care that does not include AGPs, CDC recommends the use of respirators when available.

The authors suggested that more research is needed to determine the risks associated with specific procedures and the protectiveness of different types of PPEs, as well as the extent of short-range aerosol transmission. They noted that patient source control, such as a patient wearing a mask or connected to a closed system ventilator during HCP exposure, might also reduce the risk of transmission.

“Early recognition and isolation of patients with possible infection and recommended PPE use can help minimize unprotected, high-risk HCP exposures and protect the health care workforce,” the authors concluded.


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. Morbidity and Mortality Weekly Report. Published April 17, 2020. Doi: http://dx.doi.org/10.15585/mmwr.mm6915e5

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