Adding to the spreading fear about Ebola, another diagnosis was confirmed in the United States on Thursday; this time, in New York City.

Craig Spencer, 33, was working with Doctors Without Borders in Guinea, one of the countries in which the Ebola outbreak in West Africa has been most severe. He returned to New York on October 17. He is currently placed in an isolation care unit at the Bellevue Hospital Center, and at least three people who have come into contact with him has also been placed in isolation, including his fiancée and two of his friends.

Following the medical protocols, Spencer had been taking his temperature twice every day since his return, but he had not shown symptoms until he had a 103 degree fever on Thursday morning.

Reports say that before then, Spencer traveled on multiple subway lines, took the Uber, and went to a bowling alley, and investigators are continuing their attempts to find what other places he may have been to. The bowling alley has been closed down, and officials said the driver of the Uber is not at risk of being infected.

“Ebola right now can spread fear just by the sound of the word,” said New York Governor Andrew Cuomo, trying to assure the public. “I know it’s a frightening situation … But the more facts you know, the less frightening the situation is.”

Though some express concern for riding on the same subway lines that Spencer had ridden right before his diagnosis, Dr. Mary Bassett, New York City’s health commissioner, emphasized the unlikelihood of Ebola spreading through the subway. “He did not have a stage of disease that creates a risk of contagiousness on the subway. We consider it extremely unlikely, the probability of being close to nil, that there will be any problem related to his taking the subway system,” she said.

Bellevue Hospital Center is one of eight hospitals that have been designated within the state of New York to treat Ebola patients.

Spencer is now the fourth person to have been diagnosed with Ebola within the United States, and the first in New York. Thomas Duncan, the first person diagnosed in the country, died of the disease, and the two others who have also contracted the virus are receiving treatment and are recovering. The latter two are both receiving treatment in Texas.