Were anthrax spores present, he said, the liquid would turn yellow in a day or two.

FORBES: Have You Heard the One About the Anthrax Kit?

Although vaccinated monkeys did not die from the disease after inhaling anthrax spores, they were still ill for two weeks.

BBC: Anthrax vaccine 'ineffective'

Authorities said they were checking whether an air pressure machine used to clean mail sorters may have spread anthrax spores.

CNN: Postal workers angry over response

Those who have tested positive for exposure to anthrax spores have been quick to say that they are taking the drug.

FORBES: Magazine Article

But this form of the disease is usually fatal as the inhaled anthrax spores began producing toxins that kill tissues in the chest cavity and cause bleeding in the lungs.

CNN: Cutaneous anthrax most common, most survived

Bush noted that investigators erred in the early days of the anthrax threat, believing that spores of the potentially deadly bacteria could not escape a sealed envelope.

CNN: Bush reassures Americans about anthrax

One of the few known instances of non-animal transmission occurred in the United States in 2001 when 22 people developed anthrax after being exposed to spores sent through the mail.

CNN: Anthrax

We know from studies that individuals who deal with hides of animals can be exposed to spores over an eight-hour period, and as many as 500-1000 spores inhaled over that period do not cause inhalation anthrax.

CNN: "The Secret Life of Germs" author Philip Tierno

The death rate varies among the three forms because of how the spores enter a body, according to Dr. Richard Spertzel, an anthrax expert.

CNN: Cutaneous anthrax most common, most survived