Interesting question. I'll have to think about it. My knee-jerk response is that initiation of force must be a conscious act, so my answer would be 'no'.
One thing though -- if the infected person and/or his physician were unaware that he was ill, then how would anyone know he is contagious in order to quarantine him? (Assuming that you're looking at a quarantine as a means of preventing force from being initiated).
2) Would you allow your neighbors to keep sick livestock on their property - without taking action to get them cured?