The health authorities claimed that the scientific evidence was not sufficient, which is why the research recently published by the journal ScienceDirect is relevant, which practically lets see how one of these invisible contagions happened through the air.
Was the Chinese New Years Eve Night, January 24, 2020, in a crowded Guangzhou restaurant. Hardly anyone knew then the importance of aerosols, ventilation or wearing a mask especially in closed spaces. Three families (named in article A, B and C) came out of that dinner infected. They sat at adjoining tables, with Family A in the middle. One person from this group was a 63-year-old woman from Wuhan who had started coughing and have some fever that afternoon.
A team of researchers led by Min Kang, from the Guangzhou Center for Disease Control, has recreated in an experiment how everything happened that night, thanks to the recordings of the local cameras. They put the tables and chairs back as they were, they put the 5 air conditioning systems at the same temperature as then. Sat heated mannequins to the chairs and reproduced the exhalations of air. On the tables they put bulbs to reproduce the effect of hot food. A recreation as accurate as possible to see how the aerosols of the infected person, reproduced by an emission of tracer gas, dispersed through that room without natural ventilation.
Air dynamics can be capricious, difficult to replicate in an experiment. A different current or a change in temperature can alter the result. In this case, the measurements made by the researchers showed that A cloud of infected aerosols formed right around the tables of families A, B, and C.
From that dinner they came out infected 3 of the four members of family B, 2 of the 7 of family C, and 5 members, including the original contagion, of family A. One of the infected people had been sitting at 4.6 meters away from the infected woman.
Aerosol contagion is the only sustainable hypothesis. The restaurant’s video cameras made it possible to verify that there were no other interactions between the diners, not even when they got up to go to the bathroom or when they left the premises.
The dynamics of the air currents also explains that no one sitting at other tables will be infected because what the experiments show is how a bubble consistently forms around the three affected families. The waiters remain unknown. None were infected. Perhaps because their exposure time in their comings and goings to the tables was very short. Although we must also take into account there could be some asymptomatic contagion. At that time they were not tracked.