That just makes sense. It has to be in the body fluids to spread to other areas of the body that will show symptoms.
They have no idea how and when people become contagious, its different with everybody......its still their in the blood and fecal matter and urine........
The one thing and many are guilty of it, is walking round aircraft in socks or bare foot on long flights..........do not do this. Those aircraft plane floors are perfect breeding grounds for diseases.