NEW YORK -- A hospital worker with a mysterious case of inhalation anthrax died early Wednesday, the nation's fourth fatality in a month of bioterrorism.
Kathy T. Nguyen, 61, died three days after checking herself into Lenox Hill Hospital and being diagnosed as New York City's first case of the inhaled form of the disease.
Also Wednesday, a post office spokesman said an employee at a second regional mail facility in New Jersey was suspected to have skin anthrax, and White House spokesman Ari Fleischer said a co-worker of Nguyen has a suspicious lesion that has been tested. There are no results yet, he said at the White House.
"Somebody is trying to kill the American people by sending anthrax through the mail," Fleischer said. "The president believes the actions of the government have saved lives. He regrets that these attacks have resulted in the loss of anybody's life."
Nguyen's illness, and that of a New Jersey accountant who contracted the less serious skin anthrax, complicated the investigation by raising new worries that tainted letters are contaminating other mail or that the spores are sickening people by means other than the mail.
Dr. Anthony Fauci of the National Institutes of Health said worries about "cross-contamination" -- anthrax spores sticking to pieces of mail at postal facilities -- have grown with the new cases.
"We really need to do -- the public health officials, the forensic group -- has to do a real full court press on trying to track this down. This is critical," he said on NBC's "Today" show.
The inspector in charge of the U.S. Postal Inspection Service's main forensic laboratory said Wednesday that investigators were confident there have been only three anthrax-tainted letters sent through the mail, despite concerns from medical experts that not all envelopes containing anthrax had been found.
"I still think we're dealing with three letters," said Roy W. Geffen, who runs the lab in suburban Virginia. "That's the best information we have."
The latest victims raised the number of confirmed anthrax cases to 17 nationwide since the outbreak began in early October. Ten have the inhaled form, including the four who died. The others have less-severe skin infections.
Four of those skin-anthrax cases -- and two more suspected cases -- are linked to city media outlets.
Nguyen, an immigrant from Vietnam who lived alone and commuted to the Manhattan Eye, Ear and Throat Hospital by subway from the Bronx, worked in a basement supply room. Until recently, the space had included a mailroom, but there was no evidence of any suspicious letter.
Fleischer said preliminary tests at the hospital and at Nguyen's home were negative for anthrax.
He cautioned, however, "these are preliminary negatives. There have been changes in the past" from other preliminary test results.
"Clearly in the case of Mrs. Nguyen, we do not know how she contracted the anthrax," he said.