DESCRIPTION (provided by applicant): The effectiveness in reducing influenza occurrence with use of face masks worn alone, or layered with hand hygiene will be evaluated in a randomized intervention. The study will be carried out among University of Michigan students living in University housing. Randomization will be by housing unit. In the first year, 750 students will be recruited to use face masks alone, 750 will use face masks and hand hygiene, and 750 will serve as an observed comparison group. Total number of participants will 2,250. Two small dormitories, 6 larger ones, and one complex with 10 component units have been identified as suitable for the study. Students living in each of the residence halls will be asked if they wish to participate in the study. Those giving informed consent will be asked to complete a survey each week to ascertain illness occurrence. When influenza illness is documented to be occurring in the University setting, the interventions will be implemented. During that period, the survey will be expanded to include questions on intervention use, as appropriate to the particular housing unit. Also during this period, those with illnesses meeting a case definition will be asked to provide specimens for the virus identification. This collection will not be limited to those agreeing to the use of the interventions. All living in the participating housing units will be eligible, after they give informed consent. With this sample size, it will be possible to detect a 40% reduction between those in an intervention group and the control group. Such a reduction could have a major public health impact during a pandemic. In the second year, the study can be expanded or modified based on findings in the first.