To estimate the contribution of aerosols/droplet nuclei to influenza transmission by determining the secondary attack rate (SAR) of influenza in Recipients randomised to a control arm (no intervention - allowing all modes of transmission) compared to Recipients randomised to an intervention arm (face shield and hand hygiene - allowing only transmission by aerosols/droplet nuclei) when both groups of Recipients are exposed to Donor volunteers infected with influenza via intranasal drops.