Patients infected with the Ebola virus are contagious as soon as they start exhibiting symptoms. The farther into the disease they go, the more contagious they become. This doctor would have had a low-grade fever, nausea, other digestive symptoms, headache, body aches and joint pain early on. The problem is these early symptoms can mimic other non-life threatening diseases. Given where this fellow had been, he should have quarrantined himself and been on the lookout for possible development of Ebola symptoms. His own arrogance may have killed him and infected countless other New Yorkers.
Even if he did not have a life threatening illness or disease, once a person is sick, it would be nice if they stayed home to be sick, instead of sharing it. I've sometimes called in with mild symptoms, rather than taking it to work and sharing it. Taking care of myself while the cold or flu is mild sometimes prevents it from getting severe.