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03-02-2010 | Respiratory | Article

Mask use and hand hygiene reduce incidence of influenza‐like illness

Abstract

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MedWire News: A combination of moderate face-mask use and hand hygiene can significantly reduce the incidence of influenza‐like illness (ILI) among people living in crowded conditions, say US researchers.

In February 2007, the Centers for Disease Control and Prevention developed an interim planning guide on the use of nonpharmaceutical interventions (NPIs) to mitigate an influenza pandemic. These measures include voluntary home quarantine, social distancing, personal protection (use of face masks and hand hygiene), and school dismissal.

However, Allison Aiello (University of Michigan, Ann Arbor) and team explain that the effectiveness of personal protection for reducing influenza transmission, particularly among people living in close proximity, is uncertain.

To investigate further, the team studied 1437 young adults living in university residence halls during the 2006–2007 influenza season.

Students from three residential halls were assigned to use face masks alone, face masks with hand hygiene, or no such personal protection (control) for 6 weeks. Participants in the intervention groups received detailed instruction on the correct use of hand sanitizer and face masks, which they were asked to wear as much as possible in their residence hall, and use was also encouraged outside their halls. Compliance with masks while sleeping was optional.

The incidence of influenza-like illness was ascertained weekly and cumulatively using questionnaires.

Overall, 32% of the participants developed influenza-like illness during the study period.

Analysis revealed that, during weeks 4–6, students assigned to the face masks with hand hygiene group were an estimated 35–51% less likely to have influenza-like illness than those assigned to the control group, after accounting for mask and hand hygiene compliance, alcohol use, smoking habits, physical activity, levels of perceived stress, reported influenza vaccination history, and other variables.

Students assigned to the face mask only group also showed a similar reduction in influenza-like illness during weeks 4 to 6 compared with controls, but adjusted estimates did not reach statistical significance.

Over the entire 6‐week study period, both intervention groups showed an unadjusted 10% reduction in the cumulative incidence of influenza-like illness compared with the control group, but again, this did not reach statistical significance in adjusted analysis.

Aiello and team conclude in the Journal of Infectious Diseases: “We found a significant reduction in the rate of influenza-like illness among participants randomized to the face mask and hand hygiene intervention during the latter half of this study.”

They add: “If our findings also apply to laboratory‐confirmed influenza infections, the effect on influenza transmission could be substantial, particularly early in a pandemic when vaccine supply will almost certainly be limited, as with the current H1N1 pandemic.

“Our results indicate that interventions to reduce the transmission of influenza-like illness during a winter season may have substantial effects among individuals who share crowded living conditions.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Mark Cowen

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