Using your logic everyone that rode the subway with the "last idiot" should be quarantined. How about the people they came in contact with them? How far out should we go?
I understand your opinion and respect it but this is not Russia.
I'm a lawyer, I'm fairly good at finding places to "draw the line" and avoiding mental paralysis from not containing 100% of any risk presented.
This nurse was, to use the language of churnbabychurn:
cleaning up copious amounts of bodily fluids for weeks. Not just serving tea.
I think the line should be drawn at anyone who travelled to a country with a large outbreak, but I'd certainly think it should at least include people who had direct contact.
Of course, it would contain the virus even better if we could quarantine every person on that subway, and even better if we could just quarantine everyone in the country for 21 days and then stop allowing people in from outside the country at all. But in making public policy (or your own policy), we should probably be slightly more utilitarian and also balance the cost of these policies.
The cost of quarantining everyone on that subway is very high. The cost of quarantining this one nurse is very low. It is a reasonable place to draw the line.
Some (the CDC) has maintained that the cost of quarantining the nurse is also high since it will discourage nurses from travelling to treat patients in Africa which will indirectly harm us if it causes the disease to spread further. I do not believe this; I would think that a medical professional in good faith who was willing to travel to Africa and be exposed to the virus, would also be willing to put up with a reasonable quarantine upon return. If they were actually in good faith, they would in fact insist on a quarantine upon return and would thank us for providing one, instead of threatening meaningless law suits.