It matters zero to nothing if your classmate has a virus, and your rolling with him.
Yes I have to agree with you here. The other guy is right too obviously cleaning the mats will help (all the other people and classes on mats, especially kids classes) but that's not a realistic thing either...no school is going to clean their mats 3-5 times a day.
If you are rolling with someone infected you are fucked. This is an airborne virus. You are going to be starting on knees or standing up, face to face basically, head on head wrestling, on top in guard, bottom in guard, side control, etc. You are going to be using your head as a post and plant it into the other guy's chest/head/etc. At that point you're 100% fucked unless you miraculously just don't contract it, because heavy breathing = airborne virus = you are exposed.
But what I've been saying in this thread, is that...this thread is retarded anyway. Because just look logically: This virus is airborne. Coughing, sneezing, breathing, any fraction or microscopic amount of spit flying in the air = transmission vector.
So just think about it scientifically, logically here. What puts you at more risk, the odds the 3-5 guys you drill/roll with have it, the 8-20 people in a given class, the 50-100 people using the mats in one day (cleaned or not, time elapsed for virus to die on surfaces factored).
OR going into a train, a mall, a supermarket, on a plane, in a hospital/doctor's office, a
school, bars/clubs. Any gathering of people into enclosed spaces = more risky than rolling with people at BJJ, unless you're constantly wearing a gas mask and bleaching your hands/clothes, sure.
And for the record now, South Korea (and somewhere else) has shut down public schools for children for the month of March, next month. Great idea. And proves my point as well.