Less than a month after the attacks of Sept. 11, 2001, America awoke to another form of terrorism — a biological killer sent through the mail.
Letters containing anthrax mailed to media outlets and the U.S. Senate killed five people and infected 18 others last year, terrifying the nation.
ABCNEWS' Dr. Tim Johnson checked in on some American anthrax survivors one year after the attacks, and found they're still dealing with health problems related to their exposure.
Patrick O'Donnell, David Hose and Leroy Richmond are among the rarest fraternity in America — that of the American anthrax attack survivors.
O'Donnell says he has been experiencing frequent fatigue and panic attacks, while Hose says he finds himself running short of breath. Richmond says he's been suffering from fatigue since coming in contact with spores last year.
Postal workers who handled the anthrax letters, or worked near machines that did, were affected most by the attacks.
Norma Wallace, 57, was hospitalized when she inhaled anthrax spores while handling letters at a post office in Hamilton Township, N.J. Wallace is still suffering the health effects.
"Life has not returned to normal," Wallace said. "I still have joint pain. I still have chronic fatigue. I still have memory loss."
Anthrax experts say they simply don't know what survivors like Wallace can expect in the future. Wallace says no one seems to be able to tell her when and if the symptoms will subside.
The survivors, despited their reports of ongoing illnesses are lucky. Five people, including Bob Stevens, a photo editor at the supermarket tabloid The Sun, didn't get to join their fraternity.
Stevens, 63, was the first person to die from anthrax exposure. Investigators believe he opened a poisoned letter, although the letter has never been found.
Anthrax is a colorless, odorless, tasteless bacterium that protects itself from sunlight, heat and disinfectant by forming a protective coat. With this coat, the bacterium is called a "spore."
The spores are so small that even 8,000 to 10,000 spores appear smaller than a speck of dust. This is the amount that animal studies suggest could be required for a lethal dose, although scientists are considering a much smaller dose could cause anthrax in people.
If inhaled, anthrax spores can germinate and lead to infection within one to 60 days. This is pulmonary anthrax, which usually causes death.