Sept. 18: Envelopes containing letters and granular substances are sent to NBC News in New York and the New York Post. Both are mailed from Trenton, N.J.

Sept. 22: Editorial page assistant at New York Post who opens letters to the editor notices blister on her finger. She later tests positive for skin form of anthrax.

Sept. 26: Maintenance worker at Trenton regional post office in Hamilton, N.J., visits physician to have lesion on arm treated.

Sept. 27: Teresa Heller, letter carrier at West Trenton post office, develops lesion on her arm.

Sept. 28: Erin O'Connor, assistant to NBC News anchor Tom Brokaw, notices a lesion.

The 7-month-old son of an ABC producer in Manhattan spends time at the network offices. He develops a rash, and is hospitalized with an unknown ailment soon after the visit. He is later diagnosed with cutaneous anthrax.

Sept. 30: Bob Stevens, photo editor at supermarket tabloid The Sun in Boca Raton, starts to feel ill.

Oct. 1: Erin O'Connor, the NBC assistant to anchor Tom Brokaw, goes to her doctor with a low-grade fever and a bad rash and is prescribed the antibiotic Cipro.

Ernesto Blanco, 73, an American Media Inc. mailroom employee, is hospitalized with pneumonia.

Oct. 2: At 2:30 a.m., American Media Inc. photo editor Stevens arrives at JFK Medical Center in Atlantis with 102-degree fever, vomiting and confusion. He deteriorates rapidly.

Oct. 3: Doctors determine Stevens, 63, has anthrax. He is on a respirator, being treated with intravenous penicillin.

In New Jersey, Heller, the West Trenton post office letter carrier, is hospitalized and a biopsy is performed.

Oct 4: AMI calls the U.S. Centers for Disease Control and Prevention to ask whether its Boca Raton headquarters should be evacuated. The CDC says no, and everyone continues working as usual at AMI. That afternoon, JFK Medical Center along with the Florida Department of Health's Dr. Steven Wiersma call a news conference to confirm that a patient has anthrax. They stress that it is a public health investigation and they believe it is an isolated case.

Oct. 5: Teams from the CDC fan out to Stevens' home and office. At JFK's intensive care unit, Stevens is pronounced dead, becoming the first anthrax fatality in the United States since 1976.

Oct. 7: At 7 p.m. the CDC notifies AMI that they intend to seal the building because test samples have shown anthrax spores on Stevens' computer keyboard and in the nasal passages of Ernesto Blanco, an AMI employee who delivered mail to other workers there.

Oct. 8: In Miami, the family of Ernesto Blanco is notified that Blanco has tested positive for anthrax exposure. He has no symptoms of anthrax infection. Employees of AMI line up at the Delray Health Center to be tested and to receive a two-week supply of antibiotics

Oct. 9: Letters containing anthrax addressed to U.S. Senate Majority Leader Tom Daschle and Sen. Patrick Leahy are postmarked in Trenton, N.J. The letters bear the same fictitious "Greendale School" return address and are written in all-capital block letters.

In New York, a skin biopsy is performed on the NBC employee.

In South Florida, the FBI says it found no traces of anthrax in the known places the Sept. 11 hijackers had stayed, or in Stevens' home or the places he frequented. Federal and state officials said they now believe the case is an isolated incident of "foul play." President Bush tries to assure anxious Americans that the Florida cases do not warrant national alarm.