In addition to pandemic preparedness, knowledge about the efficacy of masks and hand hygiene would also be important for inter-pandemic influenza control. In western temperate and regional subtropical countries, influenza is a major source of morbidity and mortality during the seasonal periods of epidemic circulation [8, 9] , and a number of measures are typically taken to try to reduce transmission in hospitals and elderly care homes [1] . However there are few data on the efficacy of such measures in the household, although household transmission is thought to be one of the most important settings for the community transmission of influenza [10] .