I don't think the concept of fault applies. The reality of the situation is that it is bad for the infected person to be around others until a solution is found, one way or another this problem will be dealt with. We see how the government dealt with it. It could be done better, but usually such decisions are made under uncertain conditions. Noone knows how infectious the disease is or the route by which it travels, etc. Ideally, symptomless carriers should be rewarded somehow.