A universal masking policy for healthcare providers and home care workers dramatically reduced respiratory viral infections in hematopoietic stem cell transplant (HSCT) patients, researchers report.1

Routine required mask use has been associated with some pushback in some instances, particularly when used as a policy for healthcare workers who decline flu shots. However, in this case, healthcare workers were on board with enthusiasm once they understood the risk to a vulnerable patient population.

“Everyone was very compliant and they realized the importance of the issue,” says Mitchell E. Horwitz, MD, associate professor of medicine and director of the Clinical Research Adult Blood and Marrow Transplant Program at Duke University Medical Center in Durham, NC. “These are not N95 [respirators] and uncomfortable. They are surgical masks and much easier to tolerate. Anecdotally, the head nurse believes there were fewer respiratory infections among nursing staff because they were wearing masks more frequently and there were less infections being passed from nurse to nurse.”

Parainfluenza virus 3 (PIV3) — the primary threat to this particular patient group — was reduced sharply from an infection rate of 8.3% to 2.2% following the mask intervention.

“That really is the virus that was most prevalent in our population and causing the most symptoms,” he says. “Influenza and respiratory syncytial virus are much more serious, but fortunately, not as common. Whether [this intervention] would help reduce those viruses is not clear because of the relatively low numbers, but the parainfluenza was the biggest [factor] and was really the impetus for the study.”

The surgical mask policy requires all workers in inpatient and outpatient HSCT facilities with direct patient contact to wear surgical masks regardless of symptoms or season. While standard infection control procedures are effective against respiratory infections, they may be insufficient to prevent the spread of PIV3. That is because providers and others with PIV3 may shed virus while asymptomatic, Horwitz explains.

Thus, standard droplet precautions that focus on symptomatic patients (or workers) may not be protective. Similarly, strategies that increase infection control measures during the winter influenza and respiratory syncytial virus (RSV) seasons neglect PIV3, which peaks in the summer months, he notes.

The Duke stem cell unit was hit hard with respiratory infections in 2009, leading to the creation of the new policy: All healthcare workers and caregivers of HSCT must wear a surgical mask around the patients. The masking policy was in effect year-round.

The researchers compared the infection rate from the period of 2003-2009 to the post-intervention timeframe of 2010-2014. Overall, respiratory infections dropped from a rate of 10.3% in the no-mask period to 4.4% after the policy. Significant decreases were seen for both allogeneic and autologous transplants. Again, infections due to PIV3 comprised the majority of the reduced infections.

The findings suggest that the asymptomatic workers may have spread viral infections to patients prior to the masking policy.

“Yes, that is certainly true, and it also was true of the [home] caregivers that were involved with the patient management,” Horowitz says. “When someone is going through a bone marrow transplant, at least in our program, they spend a lot of time out of the hospital. So by instituting this not only by healthcare providers, but by caregivers at home, I think that is how we were able to have this impact.”


  1. Sung AD, Sun J, Thomas S, et al. Universal Mask Usage for Reduction of Respiratory Viral Infections After Stem Cell Transplant: A Prospective Trial. Clin Infect Dis 2016; 63(8):999-1006.