"We have every reason to believe that this infection is an isolated, accidentally and naturally transmitted case," Mayor Michael Bloomberg said Wednesday at a City Hall news conference.

Vado Diomande, 44, of New York City, collapsed last week after performing in Pennsylvania, where he was in stable condition Thursday.

Health officials believe he may have inhaled spores while making the drums, a process that includes soaking hides, stretching them and scraping them to remove hair, said Dr. Lisa Rotz, a medical epidemiologist with the federal Centers for Disease Control and Prevention. She said investigators were seeking samples of the hides to test them for spores.

Doing Better Than Expected

His personal physician, Dr. Melanie A. MacLennan, said he suffered a severe skin infection in 2003 that left him hospitalized for six weeks. MacLennan told The New York Times and Daily News that Diomande was probably exposed to anthrax while in Africa that year.

This time, Diomande became ill shortly after returning from western Africa's Ivory Coast in December, officials said.

He was diagnosed with respiratory anthrax, which can be fatal, but city Health Commissioner Thomas Frieden said he was breathing on his own and appeared to be "doing better than people with respiratory anthrax usually do."

Other people, including a relative, may also have been exposed and were receiving antibiotics, Frieden said.

Federal and city officials searched Diomande's workspace and apartment and found no evidence that anthrax was produced in either location. There also was no evidence of criminal intent or terrorist connection, the mayor said.

No Terrorism Link

Anthrax spores are found in soil in many parts of the world, and livestock become infected from consuming contaminated soil or feed. People can become infected if they contact the contaminated hides or other parts.

Contracting inhalation anthrax from natural sources is rare. The last US case not linked to terrorism occurred in 1976. The victim made wool rugs as a hobby, Rotz said.

The US was put on high alert weeks after the 2001 terrorist attacks when anthrax-laced letters popped up in spots including New York City. Around the country, five people died and 17 were sickened. Investigators never determined who was responsible.

Associated Press writers Sara Kugler in New York; Mike Stobbe in Atlanta; and Genaro C. Armas in Mansfield, Pennsylvania, contributed to this report.