“…In the assessment of the contagion of saliva, it is important to consider the “ time of physical decay ” depending on the droplets size (Flügge’s droplets), the speed of emission (sneeze or cough), the moisture content in the room and the air exchange, and the “ biological decay ”, namely how long the virus keeps infecting in saliva droplets. The biological decay is caused by dehydration, ultraviolet rays, and chemical products [ 39 , 40 , 41 ]. There are some studies performed about the persistency of the 2019-nCoV in aerosol and different surfaces (plastic, steel, copper, carton) [ 24 , 42 , 43 , 44 , 45 , 46 ].…”