they were expelled. Quartz speculated that the U.S. CDC's adoption of may have stemmed from a study of SARS transmission on an airplane, published in The New England Journal of Medicine. When contacted, however, the CDC did not provide any specific information. Some have suggested that distances greater than should be observed. One minute of loud speaking can produce oral droplets with a load of 7 million SARS-CoV-2 virus per milliliter that can remain for more than eight minutes, a time-period during which many people could enter or remain in the area. A sneeze can distribute such droplets as far as or . Social distancing is less effective than face masks at reducing the spread of COVID-19. Various alternatives have been proposed for the tradition of handshaking. The gesture of namaste, placing one's palms together, fingers pointing upwards, drawing the hands to the heart, is one non-touch alternative. During the COVID-19 pandemic in the United Kingdom, this gesture was used by Prince Charles upon greeting reception guests, and has been recommended by the Director-General of the WHO, Dr. Tedros Adhanom Ghebreyesus, and Israeli Prime Minister Benjamin Netanyahu. Other alternatives include the popular thumbs up gesture, the wave, the shaka (or "hang loose") sign, and placing a palm on one's heart, as practiced in parts of Iran. School closures Mathematical modeling has shown that transmission of an outbreak may be delayed by closing schools. However, effectiveness depends on the contacts children maintain outside of school. Often, one parent has to take time off work, and prolonged closures may be required. These factors could result in social and economic disruption. Workplace closures Modeling and simulation studies based on U.S. data suggest that if 10% of affected workplaces are closed, the overall infection transmission rate is around 11.9% and the epidemic peak time is slightly delayed. In contrast, if 33% of affected workplaces are closed, the attack rate decreases to 4.9%, and the peak time is delayed by one week. Workplace closures include closure of "non-essential" businesses and social services ("non-essential" means those facilities that do not maintain primary functions in the community, as opposed to essential services). Canceling mass gatherings Cancellation of mass gatherings includes sports events, films or musical shows. Evidence suggesting that mass gatherings increase the potential for infectious disease transmission is inconclusive. Anecdotal evidence suggests certain types of mass gatherings may be associated with increased risk of influenza transmission,