LANTANA, Fla. (AP) - Health officials began tracing the steps of a Florida man to pinpoint how he became the first person in a quarter-century to contract an inhaled form of anthrax, a disease whose profile has been raised since the terrorist attacks.

U.S. officials said there was no threat of terrorism, but they dispatched investigators to North Carolina and Florida, two states where Bob Stevens has spent time in recent weeks. He was in critical condition Thursday.

"There's no need for people to fear they are at risk," Dr. Jeffrey P. Koplan, director of the Centers for Disease Control and Prevention in Atlanta, said Thursday.

Stevens, 63, is known by neighbors in this suburban town south of West Palm Beach for helping others with home repairs, his morning bike rides, and for sharing tomatoes and peppers from his garden. He is an avid outdoorsman.

Neighbors said they were worried about where he contracted the disease and whether they also could be at risk of contracting anthrax from the same source.

"Hopefully it wasn't around here," said Louis Sellitti, 33, a father of four.

Anthrax isn't contagious, but can be contracted naturally, often from livestock or soil. It has been developed by some countries as a possible biological weapon.

Koplan said a deliberate release of the germ by terrorists is one of several possibilities under investigation. "We have that on the list," he said.

"We are in a period of heightened risk and concern in this country," he said. "It's our responsibility to make sure people know what is going on and we control it as quickly as possible."

Health officials said they were tracing where Stevens had been and what he had done.

He traveled to North Carolina on Sept. 27 and left three days later because he wasn't feeling well, said Debbie Crane, spokeswoman for the North Carolina Department of Health and Human Service. He visited Charlotte, Duke University in Durham and Chimney Rock Park where he participated in outdoor activities, Crane said.

The CDC has canvassed hospitals and health departments in the two states and found no one else with similar symptoms, Koplan said.

He said the patient has no digestive symptoms that would indicate the anthrax came from drinking contaminated water, and no skin symptoms from direct contact with the germ.

The most recent previous U.S. case of anthrax was earlier this year in Texas. But that was the more common skin form, not inhalation anthrax, an especially lethal form in which the disease settles in the lungs.

During the 20th century, only 18 cases of inhaled anthrax were reported in the United States, the most recent in 1976.

Stevens was on a ventilator Thursday at JFK Medical Center in Atlantis

"We're praying that he pulls through," said Rita Stevens, a daughter-in-law who lives in Tallahassee. "We're devastated."

Neighbors said Stevens, a father of four grown children, would mow the lawn of an ill neighbor and repaired flat tires on their children's bikes. His identity was released by his employer, the supermarket tabloid The Sun, where he is photo editor.

"He helped all the neighbors whenever they needed it," said Mary Crandell. "He's just a really great neighbor. He has been for twenty-some years."

Fears that terrorists may have been planning an airborne chemical or biological attack were raised last month when it was learned that a group of Middle Eastern men - including one of the hijackers in the attack on the World Trade Center - had been asking suspicious questions about a crop sprayer at an airfield in Belle Glade, which is about 40 miles inland from Lantana.

Those fears prompted the government to ground crop sprayers after the attacks.

Anthrax causes pneumonia, and patients are treated with antibiotics. There is also a vaccine to prevent the spread of the disease, but it is available only to the military now.

Copyright 2001 The Associated Press. All rights reserved.