Let me ask ya'll nowadays sometimes out of the blue you just sneeze then nothing happens no running nose or sore throat ? Means you've just naturally purge some flu symptoms meanwhile you're asymptomatic till you get it all out of your system.
If you stay in a cluster like dorm they keep bombarding you your chance of getting 'sick' is higher that's common sense.
If we test all of us at once at least half a million can be identified.