ER's are required to treat anyone who shows up regardless of whether or not that they have health insurance. If they have ebola, are required to be put in isolation, and still don't have health insurance, they will get a bill after they get out of the hospital. If they pay for it is an entirely different story.
Or are you referring to the case of someone being suspected of ebola and need to be quarantined for three weeks while being monitored? That is a good question even if one does have health insurance. It would be nice if ones' employer considered it disability leave or something similar.