Anthrax can kill so quickly that by the time symptoms show up, it's usually too late to treat its victims, experts say.

Within one to six days after inhaling spores of the anthrax bacterium, a victim may think he's getting a common cold, with fever, fatigue and a cough. A couple of days later, he begins to have severe trouble breathing. He may start to sweat profusely and his skin can take on a bluish tint.

Within 24 to 36 hours after that, he's usually dead.

"The longer you can keep them alive and have them on antibiotics, the greater the chance of survival," said David Huxsoll of Louisiana State University. "But usually these people deteriorate very, very quickly."

The odds are better if someone realizes he has breathed in the spores and takes quick action. If a person starts taking antibiotics before any symptoms appear, the chances of surviving are "pretty good," said Huxsoll, a former commander of the Army institute charged with building defenses against biological weapons.

Without treatment, bacteria emerging from the spores quickly establish an infection in the lung and then spread rapidly through the bloodstream. The bacteria pump out a toxin, damaging body tissues. The lungs, for example, rapidly lose their ability to get oxygen into the blood.

An infected person cannot usually infect another person, Huxsoll said Thursday.