Jefferson and colleagues reviewed the literature on the effectiveness of physical interventions to reduce the transmission of respiratory viruses. The review was ambitious in scope, ranging from individually applied interventions to population-wide distancing policies. The authors have added 9 papers to their 2007 Cochrane review of 49 papers describing studies of physical interventions.1 The main conclusions continue to support the importance of physical interventions, namely that hand washing is effective in reducing the spread of respiratory infections in hospital, school and community settings; face masks and other physical barriers are …