question: Table B (available as a supplement to the online version of this article at http://www ajph org) summarizes the findings from six randomized controlled trials that examined the effectiveness of surgical masks and hand hygiene to prevent respiratory virus transmission in household and residential hall settings In a public health behavior survey conducted in New South Wales, Australia, only 58% ofthe respondents were willing to wear a surgical mask 4 In a study in which passengers in two metro stations in Mexico City, Mexico, were observed during the H1N1 epidemic in 2009, the proportion of passengers wearing a surgical mask varied between 8 9% and 76 5% 5 We note that a shift in attitudes has occurred outside east Asia as well with a new policy report in the United States recommending mask use by the general public6 and the World Health Organization conditionally recommending face mask use by asymptomatic people for mitigating the effect ofpandemic influenza (https://www who int/influenza/publications/public_ health_measures/publication/ en) After extensive promotion of hand hygiene in Hong Kong, many Hong Kong citizens had satisfactory hand hygiene practices despite lacking detailed understanding of viruses 3 For instance, hand sanitizers are commonly carried and used by Hong Kong citizens and are provided in many public places such as metro stations, shopping centers, schools, and business offices