Surgical Mask Usage Reduces the Incidence of Parainfleunza Virus 3 in Recipients of Stem Cell Transplantation

Respiratory viral infections (RVI) are frequent complications of hematopoietic stem cell transplantation (HSCT). Parainfluenza virus 3 (PIV3) in particular affects patients after HSCT, spreads nosocomially, and is associated with increased morbidity and mortality. Given the absence of proven effective treatments, prevention is key. Requiring all individuals with direct patient contact to wear a surgical mask is a simple and inexpensive intervention that may reduce droplet exposure by asymptomatic shedders and limit nosocomial spread.

We performed a prospective study to assess the impact of surgical masks.  Between January 10, 2010-January 9, 2012 (mask period), all individuals with direct patient contact, including caregivers, visitors, and medical staff, were required to wear a surgical mask when within 3 feet of a patient, regardless of suspicion of RVI. This continued until the patient returned home after HSCT. The primary endpoint was the incidence of RVI compared to the control period of December 1, 2003-November 30, 2009 (pre-mask period). A brief washout period (December 1, 2009-January 9, 2010) allowed for implementation. Standard infection prevention precautions were in place throughout both periods. Secondary endpoints include clusters of RVI, defined as 3 or more infections in a 30-day period, and death from RVI. The study was designed to detect a 40% reduction in the incidence of RVI with 90% power.

During the six-year pre-mask period, 920 patients received HSCTs. During the two-year mask period, 454 patients received HSCTs. In the pre-mask and mask groups, median age was 50 and 54 (p<0.0001) (ranges 19 to 79 and 19 to 81).  With the exception of non-Hodgkin lymphoma (21% and 15%) and plasma cell dyscrasia (32% and 46%) (p=0.004), there were no differences in disease representation.  Allogeneic HSCT constituted 41% and 33% of transplants (p=0.004). Median days at risk were 25 and 20 days (p=0.054).

The incidence of any RVI was 10.3% in the pre-mask period and 3.3% in the mask period (p<0.0001) (Table 1). Among patients who had an allogeneic HSCT, the incidence was 16.9% and 6.7% (p=0.001); among patients who had an autologous HSCT, the incidence was 5.7% and 1.6% (p=0.005). Surgical mask usage had the most pronounced affect on reducing the incidence of PIV3 (8.1% to 2.1%, p<0.0001), which was the most common virus (74% and 60% of infections), followed by RSV (16% and 13%). There were more clusters in the pre-mask period (1.7/year vs. 0.5/year). In a blinded audit by three physicians, RVI contributed to death in 1.2% of patients in the pre-mask period and 0.2% in the mask period (p=0.12). Patients with RVI required more peri-transplant care (median 76 days vs. 21 days, p<0.0001). These data suggest that requiring all individuals with direct patient contact to wear a surgical mask can reduce the incidence of RVI, particularly PIV3, during the vulnerable period following HSCT.