College students living in residency halls who wore the masks for a few hours a day and regularly used alcohol-based hand sanitizer cut their risk of coming down with flu-like illness by up to half, Dr. Allison E. Aiello of the University of Michigan in Ann Arbor and her colleagues found.

We do think it probably would generalize to other settings in which you have people living in close quarters and eating in shared facilities -- for example military barracks or nursing homes, Aiello told Reuters Health in an interview. We can probably even bring this to the household setting.

Non-drug interventions like hand hygiene and face masks are likely to be important in fighting any flu pandemic, Aiello and her team point out. During the current H1N1 epidemic, they note, vaccines were slow to arrive and use of antiviral drugs was limited.

To investigate what measures might be most effective in preventing spread of the flu, the researchers divided 1,437 college students into three groups, based on which residence hall they lived in: mask plus hand-sanitizer, face masks only, or a control group. Aiello and her team kicked off the six-week study as soon as the university confirmed the first case of influenza on campus, but continued enrolling study participants for the first two weeks.

During those two weeks, there was no difference among the three groups in the incidence of flu-like illness; this is likely because the flu season was just beginning, according to Aiello. But for the last couple of weeks of the study, she and her colleagues found that students using face masks and hand sanitizer were 35 percent to 51 percent less likely to develop flu-like illness than students in the control group.

While the face mask-only group were also less likely to catch flu-like illness than the control group, the difference wasn't statistically significant.

Aiello noted that some studies investigating measures to prevent the spread of influenza don't have people start using a particular intervention -- like face masks -- until someone in their household is already sick. Because she and her colleagues started having people use the intervention at the very beginning of flu season, they note, this fundamental study design difference may have improved our ability to identify an effect of mask and hand hygiene use, compared with studies of secondary transmission in which household members may already have been infected by the time of mask adoption.

Aiello and her colleagues are now looking at whether masks and hand sanitizers had an effect on the spread of influenza actually confirmed in a laboratory, rather than less specific flu-like illness.

SOURCE: Journal of Infectious Diseases, February 15, 2010.

Michigan Medicine