Hong Kong Respiratory Medicine

Benjamin J. Cowling, BSc, PhD; Kwok-Hung Chan, BSc, PhD; Vicky J. Fang, BSc, MPhil; Calvin K.Y. Cheng, BSc, MMedSci; Rita O.P. Fung, BNS; Winnie Wai, BNS; Joey Sin, BNS; Wing Hong Seto, MBBS; Raymond Yung, MBBS, MPH; Daniel W.S. Chu, MBBS; Billy C.F. Chiu, MBBS; Paco W.Y. Lee, MBBS; Ming Chi Chiu, MBBS; Hoi Che Lee, MBBS; Timothy M. Uyeki, MD, MPH; Peter M. Houck, MD; J.S. Malik Peiris, MBBS, DPhil; and Gabriel M. Leung, MD, MPH; 6 October 2009 | Volume 151 Issue 7

Background: Few data are available about the effectiveness of nonpharmaceutical interventions, such as hand hygiene and facemasks, for preventing influenza virus transmission.
Objective: To investigate whether hand hygiene and use of facemasks prevents household transmission of influenza.

Design: Cluster randomized controlled trial. Randomization was computer generated; allocation was concealed from treating physicians and clinics and implemented by study nurses at the time of the initial household visit. Participants and personnel administering the interventions were not blinded to group assignment.

Setting: Households in Hong Kong.

Patients: 407 people presenting to outpatient clinics with influenza-like illness who were positive for influenza A or B virus by rapid testing (index patients) and 794 household members (contacts) in 259 households.

Intervention: Lifestyle education (control) (134 households), hand hygiene (136 households), or surgical facemasks plus hand hygiene (137 households) for all household members.

Measurements: Influenza virus infection in household contacts, as confirmed by reverse transcription polymerase chain reaction (RT-PCR) or diagnosed clinically after 7 days.

Results: Sixty (8%) household contacts in the 259 households had RT-PCR–confirmed influenza virus infection in the 7 days after intervention. Hand hygiene without or with facemasks seemed to reduce influenza transmission, but the differences in transmission compared with the control group were not statistically significant. In 154 households in which interventions were implemented within 36 hours of symptom onset in the index patient, transmission of RT-PCR–confirmed infection seemed to be reduced, an effect attributable to reductions in infection among participants using facemasks plus hand hygiene (adjusted odds ratio, 0.33 [95% CI, 0.13 to 0.87]). Adherence to interventions was variable.

Limitation: The delay from index patient symptom onset to intervention and variable adherence may have mitigated intervention effectiveness.

Conclusion: Hand hygiene and facemasks seemed to prevent household transmission of influenza virus when implemented within 36 hours of index patient symptom onset. These findings suggest that nonpharmaceutical interventions are important for mitigation of pandemic and interpandemic influenza.

Primary Funding Source: Centers for Disease Control and Prevention.

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