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.
Fault definitely applies. Maybe not the first time the disease gets passed on, but once they've been told they're contagious, it's on them to see that it doesn't happen again.
I agree somewhat. It is also on others to create an environment that allows the information to flow as accurately as possible about who may have bad disease X, so that anti-social behaviour by the infected person is not significant point of failure in the system, while not leading to undue ostracization.