Want to Limit Respiratory Virus Infections? Mask and Test in Hospitals

Stopping universal masking and SARS-CoV-2 testing in hospitals led to a surge in hospital-onset respiratory viral infections relative to community infections, a cohort study found.

After these safeguards were removed, there was a 25% jump in hospital-onset respiratory viral infections compared with the preceding Omicron-dominant period (RR 1.25, 95% CI 1.02-1.53), reported Theodore Pak, MD, PhD, of Massachusetts General Hospital in Boston, and colleagues.

When hospital staff began masking again, the rates of hospital-onset respiratory viral infections decreased by 33% (RR 0.67, 95% CI 0.52-0.85), they wrote in a JAMA Network Open research letter.

In May 2023, 10 Mass General Brigham hospitals stopped pandemic-era precautions of testing patients for SARS-CoV-2 upon admission and requiring masking. During universal testing, SARS-CoV-2 tests were collected for 92.9% of patients compared with 26.5% after universal testing ended.

“When our healthcare system stopped universal admission testing and masking there was, after adjustment, a 25% increase in hospital-onset respiratory viral infections, which includes COVID, flu, and RSV [respiratory syncytial virus], compared to before,” Pak said.

“This sort of gave us a natural opportunity to look at a before-and-after then in terms of rates of hospital-onset COVID, adjusting for all the other things that we could in this kind of study, particularly community rates of COVID infection,” Pak told MedPage Today.

In January 2024, Mass General Brigham reinstituted masking for healthcare workers but not patients, which led to hospital-onset respiratory viral infections declining by one-third.

“This is a helpful trend to look at because it suggests that these interventions, when you stop them, are associated with increases in hospital-onset respiratory viruses, and then when you restart them, they’re associated with a decrease,” Pak said.

During the study time period, there were 641,483 total hospital admissions and among them, 30,071 community-onset and 2,075 hospital-onset SARS-CoV-2, influenza, and RSV infections.

Unadjusted analyses revealed that the mean weekly ratio between hospital-onset and community-onset infections rose from 2.9% before Omicron dominance to 7.6% during Omicron dominance (95% CI 6%-9.1%). After universal testing and masking ended, the ratio surged to 15.5% (95% CI 13.6%-17.4%). It dropped to 8% after healthcare workers began masking again (95% CI 5%-11%).

Pak noted that as hospitals enter another winter respiratory virus season, many are thinking about curbing infections.

“Our study would support the use of targeted universal masking, which I think is potentially more palatable from a cost perspective than re-instituting universal testing, and it is something that we will hopefully do in our own hospital system as well as case counts pick up again,” he said.

The research “clearly demonstrates the value of public health tools — testing and masking — that can be used to reduce the spread of SARS-CoV-2,” especially in healthcare settings, noted Becky Smullin Dawson, PhD, MPH, of Allegheny College in Meadville, Pennsylvania, who wasn’t involved with the study.

“We know how to prevent the spread of SARS-CoV-2,” she added. “When there is increased spread of SARS-CoV-2 in our communities, physicians and healthcare facilities would be wise to implement policies requiring masking of providers and/or testing of all patients seeking care.”

Pak and co-authors analyzed patients admitted to 10 Mass General Brigham hospitals (two tertiary hospitals, seven community hospitals, and one eye and ear hospital) from November 2020 to March 2024.

They examined data in four time periods: pre-Omicron variant with universal testing and masking, Omicron with universal testing and masking, Omicron without universal testing and masking, and Omicron after restarting masking for healthcare professionals only.

Hospital-onset infections of SARS-CoV-2, influenza, and RSV were identified as the first positive polymerase chain reaction (PCR) test more than 4 days after admission. Community-onset infections were considered the first positive test within 4 days.

The researchers also analyzed 100 randomly selected hospital-onset SARS-CoV-2 cases admitted after the end of universal testing to assess whether community-onset cases were misclassified. Among these cases, 89% had new symptoms, 27% had known exposure, 80% had a PCR cycle threshold of 30 or less, and 97% met at least one preceding criteria. Eight died in the hospital.

Pak and colleagues acknowledged that their analysis was limited by a “lack of concurrent controls, possible variations in compliance, difficulty disentangling effects of testing vs masking, and potential case misclassification.” Chart reviews suggested, however, that most hospital-onset cases were true acute cases.

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