The employee was identified as a 35-year-old woman, whose name was withheld at her request. She has no symptoms and is receiving antibiotics to prevent illness. She tested positive after being screened with nearly 1,000 other employees or visitors to the newspaper company office building.
Any evidence of anthrax appears limited to the three-story Boca Raton headquarters of America Media Inc., owners of several tabloid newspapers, said Acting U.S. Attorney Guy Lewis. Investigators have all but dismissed the possibility that the three employees picked up anthrax outside the building from contact with animals or tainted soil.
"It is now a criminal investigation," said Lewis. "We have mobilized the full and complete resources of the federal and state governments. We are coming together to fight this problem."
Included are investigators from the FBI, the U.S. Attorney's Office, the U.S. Department of Justice, Florida law enforcement, the Centers for Disease Control and Prevention and the state health department.
Last Friday, Robert Stevens, 63, a photo editor at The Sun tabloid, died of inhalation anthrax, the most severe form of the disease. Spores were found on his keyboard when health investigators began taking samples from air ducts and surfaces throughout the building.
On Monday, federal officials said they were strongly considering the possibility of criminal activity after a mailroom employee, 73-year-old Ernesto Blanco, tested positive for spores. He was being treated at a Miami hospital for an unrelated illness, and the anthrax spores were cultured from a nasal swab.
By last night, about 1,000 employees, family members and visitors to the building had been tested for anthrax exposure and given antibiotics. Dr. John Agwunobi, the Florida health secretary, said that results had come back from 700 of the people - and only one, the unidentified woman, had tested positive. Test results from the other 300 are expected in a day or two, he said.
"Anthrax is not contagious," he said, seeking to reassure the public. "One of the messages today ... is that all evidence to date indicates that the anthrax issue is limited to the AMI building."
The woman worked in the same general vicinity as the two men, Pesquera said. Investigators are going back into the building to conduct more tests because of the new exposure.
The building remained cordoned off with yellow police tape yesterday. After it was sealed Monday, American Media Inc. moved employees to offices in nearby Delray Beach and Miami to continue publishing their weekly supermarket tabloids, including The Sun, The National Enquirer and Weekly World News. County health officials ordered the Boca Raton headquarters shut down for at least 30 days for testing and possible decontamination.
Anthrax is a bacterial disease that afflicts livestock as well as humans who have been exposed to infected animals. People generally contract the inhalation form by breathing spores from dead carcasses, wool, hides and soil. It is an extremely rare disease, with only 18 cases in the United States in this century. The most recent case occurred in California in 1976.
Experts, however, have placed anthrax high on the list of potential biological weapons. This is based largely on information that the former Soviet Union developed anthrax as a biological weapon, and that Iraq as well as other rogue nations have acquired it for their use. In 1979, an accidental release of anthrax from a Russian weapons facility killed 68 people who lived downwind.
A senior health official yesterday sought to allay fears that the Florida employees were victims of bioterrorism.
"If this was a massive exposure, there should be lots of people sick. We are not finding that," Dr. Scott Lillibridge, U.S. Health and Human Services Secretary Tommy Thompson's special assistant for bioterrorism, told members of Congress in Washington.
Finding the source of the anthrax in Florida won't be easy. Hundreds of laboratories in the United States and around the world have stored it for research. Scientists keep the bacteria in refrigerated cultures so they can conduct research into treatments, vaccines and the basic properties of anthrax.
Until rules were tightened in 1997 in the United States, laboratories everywhere freely traded anthrax bacteria. The practice enabled scientists to confirm each other's findings, standardize their methods and test treatments against a variety of strains. But now U.S. labs must be certified to handle anthrax and cannot send their holdings to unauthorized recipients.
"There are really stringent controls now," said Cheryl Loeb, a research associate at the Monterey Institute of International Studies. Even so, she said, it would be fairly easy for terrorists to obtain anthrax either by stealing it from a U.S. lab or by getting it from a country where standards are more relaxed.
"You can hide it in any little thing," said Greg Evans, director of the Center for the Study of Bioterrorism and Emerging Infections at St. Louis University. "It's also reportedly available on black markets outside of this country."
Investigators hope that identifying the particular anthrax strain used in Florida will tell them something about its origins. There are dozens of known strains, each with its unique genetic blueprint. Investigators in the Florida case have determined that Stevens and Blanco were exposed to the same strain, though they have yet to identify the precise one. That could take weeks, they said.
Scientists working for the federal Centers for Diseases Control and Prevention are trying to identify the strain by sequencing its genes and then finding a match with a strain that has been previously sequenced and catalogued.
Yesterday, attention focused on news reports that the Florida employees may have been exposed to a strain that had been identified by Iowa State University in Ames in the 1950s. The so-called Ames strain has been shared with anthrax researchers across the country, and has become one of the most widely held strains in the United States.
In past years, the U.S. Army Medical Research Institute of Infectious Diseases at Ft. Detrick used the strain to test a vaccine that was developed for military personnel. Army scientists exposed vaccinated animals to the Ames strain to see if the vaccine was effective.
The mystery of the Florida anthrax exposures has prompted rumors, false alarms and runs on antibiotics in recent days. Last night, Agwunobi, the Florida health secretary, said that Stevens should be remembered amid the panic.
"These are . . . our neighbors, our friends," said Agwunobi.
In Delray Beach yesterday, several hundred people attended a memorial service for Stevens. Anthrax was never mentioned, and speakers instead recalled the photo editor's love of fishing and his perpetual smile.
"He's just a very, very decent human being," said Bennet Bolton, a senior writer for The National Enquirer. "I don't think he ever had an unkind word to say to anybody, or even had a bad thought."
Sun staff writer Tom Pelton and wire services contributed to this article.