A doctor who recently returned to New York City from a Doctors Without Borders mission in western Africa — and who also went bowling the night before — has tested positive for the Ebola virus after developing a high fever, according to ABC News. Identified as Dr. Craig Spencer by the New York Times, the confirmation of infection may have large implications for the nation’s biggest city:

The doctor, Craig Spencer, was rushed to Bellevue Hospital on Thursday and placed in isolation while health care workers spread out across the city to trace anyone he might have come into contact with in recent days. A further test will be conducted by the federal Centers for Disease Control to confirm the initial test.

While officials have said they expected isolated cases of the disease to arrive in New York eventually, and had been preparing for this moment for months, the first case highlighted the challenges surrounding containment of the virus, especially in a crowded metropolis.

Even as the authorities worked to confirm that Mr. Spencer was infected with Ebola, it emerged that he traveled from Manhattan to Brooklyn on the subway on Wednesday night, when he went to a bowling alley and then took a taxi home.

The next morning, he reported having a temperature of 103 degrees, raising questions about his health while he was out in public.

Spencer worked in Guinea, one of the Ebola-impacted nations that has officials worried. Apparently it didn’t worry Spencer enough to self-isolate during the potential incubation period, which raises a whole lot of questions about the CDC’s latest approach to dealing with travelers from western Africa. They expect to control the potential spread of the disease by asking them to take their temperatures for 21 days and keep from being in public too much. If a health professional who’s had experience with Ebola can’t follow those guidelines, why should we expect anyone else to follow them?

Now we have a fresh case in the most populous city in the nation, and the potential for hundreds of contacts thanks to the subway ride, the cab, and the use of the bowling alley. Did he have a drink at the bowling alley? Eat food? Did wait staff handle any glasses or dishes? Did he use rental shoes and house bowling balls?

Before news of the positive test was reported, ABC News told people that they shouldn’t worry too much until more was known. It now seems that New Yorkers really do have something to worry about, perhaps especially that health-care professionals seem to be rather nonchalant about risks.

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Update: We should note that Dr. Spencer put his life on the line to help people in Guinea, a courageous effort that deserves recognition. It doesn’t change the fact that running around on public transportation within the incubation period to go bowling seems very irresponsible — and if a doctor can’t be disciplined enough to self-isolate, those with less understanding of the issues probably won’t be either.