A new report shows the second-year results (2007-2008) of the ground-breaking U-M M-Flu study found up to a 75 percent reduction in flu-like illness over the study period when using hand hygiene and wearing surgical masks in residence halls, said Allison Aiello, associate professor of epidemiology in the U-M School of Public Health. Aiello and Dr. Arnold Monto, SPH professor of epidemiology, are co-principal investigators of the M-Flu study.

While the study also showed a 43 percent reduction in the rate of flu, it wasn't statistically significant. Students were more likely to report influenza-like symptoms than to provide laboratory samples for confirmed cases, Aiello said. "This might have impacted our power for detecting significant differences in confirmed flu," she said.

The results from both years found no significant reduction in symptoms in mask use alone, which suggests masks and hand hygiene should be used together, she said.

At the beginning of a pandemic, vaccines probably won't be available immediately so one of the first lines of defense to stop the spread of illness will be non-pharmaceutical interventions like hand hygiene and face masks. The M-Flu results bode well for these types of non-pharmaceutical interventions in the community setting for pandemic preparedness, Aiello said.

"This means masks and hand hygiene may be a good measure for preventing transmissions in crowded living quarters," said Aiello. "In a pandemic situation where compliance may be significantly higher than in controlled studies, masks and hand hygiene together may have even higher preventative implications."

The M-Flu study was the first of its kind and received international exposure when launched in 2006. The team of M-Flu researchers recruited more than 1,000 students in U-M residence halls. The students were assigned to groups who wore masks, wore masks and practiced hand hygiene, or did neither. They were monitored for the presence of flu symptoms or the flu.