An important ethical consideration is that households randomised to the control intervention might be considered to have less benefit from the trial than those assigned to the mask or hand washing interventions. However we note that there is little evidence that masks or hand washing can reduce influenza transmission, whereas this study will provide that evidence. Further, the participation of a control arm is essential to allow estimation of the effect of the interventions, given the lack of localspecific data on the SAR in typical circumstances. Thus we believe that those in the control arm, as the whole of society, will still benefit indirectly from this research.