Fearing the inadvertent spread of COVID-19 by health care workers, patients, and visitors, the Centers for Disease Control and Prevention (CDC) and the Joint Commission both recommended last April that anyone working in or entering a health care facility be required to wear a face covering. Injunctions for universal masking were thus standard within weeks of COVID-19 taking hold in the United States, although implementation was hindered by a shortage of masks and other protective equipment.

Figure. Noah Wachtel, an RN at Stanford Hospital in Stanford, California, takes a nasopharyngeal sample from fellow RN Scott Gordon during staff testing for COVID-19. Photo by Karl Mondon / MediaNews Group / The Mercury News via Getty Images.

A month later, the CDC reported that more than 62,000 health care workers had tested positive for COVID-19 and 231 had died, although the numbers were likely much higher because of spotty data collection. Indeed, a survey around the same time by National Nurses United (NNU) found that 84% of nurses had not been tested.

By September, NNU's mortality tracking showed that more than 1,700 health care workers had died of COVID-19, including at least 223 nurses. The union blamed continuing shortages of personal protective equipment, infrequent testing of staff in health care facilities, and a lack of timely information about viral spread and necessary protective measures.

The CDC, meanwhile, shed light on yet another factor in COVID-19 transmission among frontline health care workers: poor adherence to mask protocols. Reporting in the September 4 Morbidity and Mortality Weekly Report, the CDC said tests at 13 academic medical centers between April and June of 3,248 workers found that of the 6% who tested positive for antibodies to COVID-19, nearly 30% were asymptomatic and did not know they were infected-and likely infectious to others. Prevalence of antibodies was also found to be higher (9%) among health care workers who said they did not always wear a mask in interactions with patients than among those who did (6%).

Backed by this evidence, and the inherent danger to coworkers and patients of contact with unmasked clinical personnel who could have asymptomatic COVID-19, the CDC reiterated its call for universal use of face coverings in health care facilities and frequent testing to mitigate infection transmission in these facilities.-Frank Brodhead