> 4. (This is the big one) It would spread when the carrier was asymptomatic.

This was also quickly found to be false. From memory the spread was 98.8% symptomatic, 1.2% pre-symptomatic, and 0% symptomatic. Granted you can't tell pre-symptomatic from asymptomatic beforehand, but with such a low proportion of infections being in that category it shouldn't have been a concern.