Regarding infectivity, even if norovirus infection is possible via inhalation of airborne droplets, the infection risk associated with the airborne route is not comparable to that of the fomite route. Viruses with high survivability on environmental surfaces usually have a higher exposure dose via the fomite route than that via the airborne route . Moreover, unlike some respiratory viruses such as influenza , noroviruses should exhibit the same dose-response parameters for the airborne and fomite routes. The corresponding exposure site of norovirus, a gastrointestinal virus, is the gastrointestinal tract. The proposed airborne transmission would require inhaled aerosol droplets to be deposited in the upper respiratory tract and then be swallowed along with respiratory mucus .