Previous studies have tentatively suggested that prophylaxis with amantadine, rimantadine, and the neuraminidase inhibitors oseltamivir (Tamiflu ® ) and zanamivir (Relenza ® ) are effective in reducing influenza transmission in households [11, 12] . Vaccination is known to be an effective preventative measure [13] provided that the at least one of the vaccine strains closely matches the circulating strain [14] . Protective interventions at the personal level to reduce influenza transmission such as wearing masks and improving hand hygiene are often recommended [15] but few studies have investigated the efficacy of these measures outside nosocomial settings in a rigorous manner. Influenza is thought to be mainly transmitted through airborne droplet nuclei [16] but to a significant extent also spread by hand and surface transfer [17] . Some studies have suggested that transmission of upper respiratory tract infections was reduced after household-based hygiene interventions [18] [19] [20] , while a recent case-control study has suggested that masks and hand-washing may have been effective in reducing the transmission of SARS in a hospital setting [21] . A recent population study has suggested that improved hygiene measures and decreased community mixing during the SARS outbreak in Hong Kong resulted in reduced incidence of respiratory viral infections [22] .