Authorities said Wednesday the infection appeared to be accidental — not terrorism — and did not pose a serious public health threat.
Vado Diomande, 44, had traveled recently to the west coast of Africa and fell ill in Pennsylvania last week shortly after he returned to this country with some goat hides, authorities said.
It was not clear whether Diomande came into contact with the deadly substance in Africa or in this country. But Mayor Michael Bloomberg said it was related to his job making drums from animal skins.
At least four other people may have been exposed to anthrax spores, including a family member of the infected man who worked with the hides, 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 and in his Manhattan apartment. Police said there was no evidence that anthrax was produced in either location.
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.
Dr. Lisa Rotz, a medical epidemiologist with the federal Centers for Disease Control and Prevention, said health officials believe Diomande may have inhaled the spores in a process that includes soaking the hides, stretching them and scraping them to remove hair.
She said investigators are seeking samples of the hides to test for spores.
The mayor said Diomande was recovering in a hospital in Sayre, Pa., after collapsing during a performance with a dance company. Pennsylvania health officials and the CDC confirmed the case as inhalation anthrax on Wednesday.
Anthrax infections must be treated early with antibiotics for the best chance of recovery. The inhalation form of the disease has a fatality rate of about 75 percent, even with antibiotics.
Frieden said Diomande was breathing on his own and appeared to be "doing better than people with respiratory anthrax usually do."
Diomande has been a dancer and drummer since he was a child, according to a Web site for his dance troupe. When he was a teenager he danced with the National Ballet of the Ivory Coast and toured all over the world. He founded his own dance company in 1989, the Web site said.
Authorities said they were not concerned that the transport of the hides or the finished drums to the U.S. posed any health risk, because they believe Diomande was infected while treating and working with the materials.
The U.S. Customs and Border Protection department says in its travel guidelines that the importation of animal products is "severely restricted," but it was unclear late Wednesday what policies governed goat skins.
At the Pennsylvania university where Diomande collapsed, students were informed about the anthrax case but were assured they were not in danger. About 100 people attended the performance, according to Terri Day, a university spokesman.
Wednesday evening, some 75 people attended a question-and-answer session in the university's auditorium where officials repeated their assurances that no one was in danger of being infected with anthrax.
"There is no chance of transmission occurring," state Health Department spokesman Troy Thompson told the crowd.
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.
That same year, a woman was hospitalized in Vancouver, British Columbia, with skin anthrax on her palm, which she contracted while handling animal hides during a drum-making class.
The last case of inhalation anthrax not linked to terrorism occurred in 1976. The victim made wool rugs as a hobby, Rotz said.