"We do have other individuals who are reporting skin lesions or other exposure circumstances that are under active investigation," said Dr. Julie Gerberding of the CDC. They are linked to the Florida and New York exposures, she said.
The unnamed woman, whose job includes handling Rather's mail, was being treated with antibiotics and was said to be recovering. Rather said she never even took a sick day.
CBS News President Andrew Heyward said, "She's doing fine, she feels great."
Although his assistant had the primary responsibility for opening his mail, Rather said "she has no memory of anything in the mail that raised any suspicion whatsoever."
"We make no assumptions about how she contracted this," Rather said. Police, however, are operating on the theory that the anthrax entered the building in the mail.
Heyward said that because no one else at CBS has shown any symptoms, only Rather's assistant would need to take antibiotics. The CBS offices were open and operating normally, although mail security procedures had been tightened.
Dr. Stephen Ostroff of the CDC, said: "The risk currently in this building is essentially negligible." Ostroff said the epidemiological investigation at CBS is continuing. But so far, "the pattern here appears to be essentially identical" to those at NBC and ABC.
In each news office, a single case of anthrax skin infection resulted from apparent contact with anthrax spores. The only anthrax-containing letter recovered in New York, however, was the one at NBC addressed to Brokaw. That letter was disguised as a letter from schoolchildren, and was postmarked in Trenton on Sept. 16.
Acting New Jersey Gov. Donald T. DiFrancesco announced yesterday that the mail carrier had tested positive for the skin form of anthrax. A second employee - a maintenance worker at the regional center - was being tested for suspected exposure to the bacteria.
Both were being treated with antibiotics, and "both are doing well," DiFrancesco said. No other anthrax cases have been reported at the facility.
In Washington, after several days that produced sometimes-conflicting information from government officials, Bush administration officials tried yesterday to reassure a nervous city and nation by showing a united front.
"There has been some concern about mixed messages," said the newly appointed homeland security director, Tom Ridge. The former Pennsylvania governor held a morning news conference with officials from across the federal government, including the Justice and Defense departments, to signal that the situation is under control.
He said authorities are taking broad steps to protect an unnerved nation.
"We are more vigilant today, and continue to get more vigilant every day as we assess different risks that might present themselves in this country," he said.
The Postal Service announced that it was sending postcards to every U.S. household offering tips about how to handle and screen suspicious mail. "We believe the mail is safe," said Postmaster General Jack Potter.
On Capitol Hill, officials reported no new cases of anthrax exposure beyond the 31 announced Wednesday. Deputy Surgeon General Kenneth Moritsugu said environmental sweeps were under way in the Capitol and in the House and Senate office buildings. No results were available yesterday.
The House of Representatives was shuttered, and nearby congressional office buildings were dark as investigators searched for suspect mail or traces of anthrax. Senators, who had vowed to keep their chamber open, scrambled to find places to work with their offices closed.
House leaders defended their decision to shut down a day before the scheduled weekend break, even as federal health officials were saying that the contaminated areas on Capitol Hill appeared to be confined to two floors, in one wing of the Hart Senate office building.
"People have asked me all day, 'Well, what message did this send to the terrorists?'" said House Minority Leader Richard A. Gephardt, a Missouri Democrat. "Well, what message would it send to the terrorists if we stupidly put people back in harm's way, to be infected by anthrax? That hardly, to me, is an intelligent response."
Ashcroft said federal prosecutors are moving aggressively against malicious pranksters. Five people have been charged with making threats or lying to federal agents. Ashcroft said the hoaxes are wasting public resources and creating "illegitimate alarm at a time of legitimate concern." Since Oct. 1, the FBI has responded to more than 3,300 threats involving chemical or biological agents - 10 times the normal level.
Yesterday, authorities in Kenya, in East Africa, said that white powder found in a letter mailed from Atlanta had tested positive for anthrax. Two other suspicious envelopes - one from Pakistan and the other mailed within Kenya - were being tested. Officials said the first letter was mailed to a Nairobi businessman three days before the Sept. 11 attacks. It arrived in Kenya on Oct. 9, and was opened two days later.
Wire reports contributed to this article.