Facemasks and hand hygiene to prevent influenza transmission in households: a cluster randomized trial.

BACKGROUND

Few data are available about the effectiveness of nonpharmaceutical interventions 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. (ClinicalTrials.gov registration number: NCT00425893)

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 contacts, as confirmed by reverse-transcription polymerase chain reaction (RT-PCR) or diagnosed clinically after 7 days.

RESULTS

Sixty (8%) contacts in the 259 households had RT-PCR-confirmed influenza virus infection in the 7 days after intervention. Hand hygiene with or without facemasks seemed to reduce influenza transmission, but the differences compared with the control group were not 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 reduced, an effect attributable to fewer infections among participants using facemasks plus hand hygiene (adjusted odds ratio, 0.33 [95% CI, 0.13 to 0.87]). Adherence to interventions varied.

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.