Journal of Infectious Diseases
15 February 2010 Volume 201, Number 4
Unmasking the Confusion of Respiratory Protection to Prevent Influenza-Like Illness in Crowded Community Settings
Titus L. Daniels and Thomas R. Talbot
…Fortunately, several well-designed in vivo studies have now been published that conclude there is no significant advantage of one mask type over another for respiratory protection against influenza or ILI. Loeb et al  conducted a noninferiority randomized, controlled study of mask use among nurses in Ontario, Canada, which demonstrated that the attack rate of laboratory-confirmed influenza was not different between those who wore facemasks and those who wore N95 respirators as respiratory protection (23.6% vs 22.9%, respectively). Although unable to demonstrate a protective benefit of mask use in households, MacIntyre et al  did note that adherence to mask use (face mask or N95 respirator) was associated with a reduction in ILI (hazard ratio, 0.26; 95% CI, 0.09–0.77).
Taken together with the Aiello et al  study, these data suggest that influenza transmission and ILI can be effectively interrupted with the use of a face mask and hand hygiene in settings of close contact. In addition, these data could inform the ongoing debate concerning respiratory protection for HCWs. Although the majority of data supporting prevention of influenza transmission with face masks has been derived from community sites, interactions between HCWs and patients are generally of a magnitude similar to what would be encountered in domestic settings. One could even argue that the household setting poses greater risk of transmission as a result of continued, prolonged exposure, whereas most HCW encounters with patients are brief, albeit possibly more frequent.
Aiello et al  have conducted a well-designed cluster randomized study demonstrating that use of a face mask combined with hand hygiene in a crowded community setting is helpful in preventing ILI. Although it would be difficult to extrapolate these data to the general public in noncrowded conditions (ie, nonresidential settings), these data can inform policy makers on the recommendations for mask use in community settings and perhaps other settings (eg, health care institutions)…
Mask Use, Hand Hygiene, and Seasonal Influenza-Like Illness among Young Adults: A Randomized Intervention Trial
Allison E. Aiello,1,2; Genevra F. Murray,3; Vanessa Perez,1,2; Rebecca M. Coulborn,1,2; Brian M. Davis,1,2; Monica Uddin,1,2; David K. Shay,4; Stephen H. Waterman,4 and
Arnold S. Monto,1
1Department of Epidemiology and 2Center for Social Epidemiology and Population Health, School of Public Health, University of Michigan, Ann Arbor, Michigan; 3Department of Sociology, Anthropology, and Social Work, University of South Alabama; 4Centers for Disease Control and Prevention, Atlanta, Georgia
Background.During the influenza A(H1N1) pandemic, antiviral prescribing was limited, vaccines were not available early, and the effectiveness of nonpharmaceutical interventions (NPIs) was uncertain. Our study examined whether use of face masks and hand hygiene reduced the incidence of influenza-like illness (ILI).
Methods.A randomized intervention trial involving 1437 young adults living in university residence halls during the 2006–2007 influenza season was designed. Residence halls were randomly assigned to 1 of 3 groups—face mask use, face masks with hand hygiene, or control— for 6 weeks. Generalized models estimated rate ratios for clinically diagnosed or survey-reported ILI weekly and cumulatively.
Results.We observed significant reductions in ILI during weeks 4–6 in the mask and hand hygiene group, compared with the control group, ranging from 35% (confidence interval [CI], 9%–53%) to 51% (CI, 13%–73%), after adjusting for vaccination and other covariates. Face mask use alone showed a similar reduction in ILI compared with the control group, but adjusted estimates were not statistically significant. Neither face mask use and hand hygiene nor face mask use alone was associated with a significant reduction in the rate of ILI cumulatively.
Conclusions.These findings suggest that face masks and hand hygiene may reduce respiratory illnesses in shared living settings and mitigate the impact of the influenza A(H1N1) pandemic.
Trial Registration.ClinicalTrials.gov identifier: NCT00490633.