Authorities said Wednesday the infection appeared to be accidental — not terrorism — and did not pose a serious public health threat.
The 44-year-old man had traveled recently to the west coast of Africa and fell ill in Pennsylvania last week shortly after his return, authorities said.
It was not exactly clear how he came into contact with the deadly substance, or whether it happened in Africa or in this country. But aides to Mayor Michael Bloomberg said it was related to his job as a drum maker who worked with raw animal hides.
At least four other people may have been exposed to anthrax spores, and three were being treated with antibiotics, city Health Commissioner Thomas Frieden said.
"Every indication suggests that this is naturally occurring anthrax," Frieden said.
Authorities were also screening for contaminants at the man's rented work area in Brooklyn, his vehicle and his Manhattan apartment, Bloomberg said.
Anthrax spores are found in soil in many parts of the world, and livestock can become infected by eating contaminated soil or feed. People can then pick up the infection if they come into contact with contaminated hides or other animal parts.
"It is actually a common occupational hazard among people who work with skins and hairs of animals from Africa, specifically cattle," explained Dr. Stephanie Factor, an infectious disease specialist at Mount Sinai Medical Center in New York City.
Aides to the mayor said the man was recovering in a hospital in Sayre, Pa., after collapsing during a performance with a dance company. Pennsylvania health officials and the Centers for Disease Control and Prevention confirmed the case as inhalation anthrax on Wednesday, the mayor said.
Weeks after the 2001 terrorist attacks, the nation was on high alert as anthrax-laced letters surfaced in several places, including New York City. NBC anchorman Tom Brokaw, two U.S. senators and the offices of the New York Post were among the targets.
The anthrax attacks killed five people across the country and sickened 17. The attacks are still unsolved.