Unlocking the Mysteries of Anthrax

Although anthrax is the newest weapon Americans’ fear, the bacterium and the disease it causes are of ancient origin.

The bacterium that causes the disease, bacillus anthracis, is found naturally in soil throughout the country. Most cases of anthrax until this month have been caused by exposure to parts of infected animals.

The disease takes three distinct forms. The cutaneous form of anthrax occurs when bacterial spores enter the body through cuts in the skin. The infection begins as a bump that resembles an insect bite but within days expands into an ulcer about an inch in diameter. This form of the disease is easily treated with antibiotics.

Inhalation anthrax is by far the most deadly form of the disease.

Upon inhalation of at least 8,000 to 10,000 spores, the bacteria is transported to lymph nodes and then to the blood. It produces a toxin that causes massive cell death. This form of the disease begins with symptoms similar to a common cold.

Coughs and sneezes may be followed by an apparent period of recovery before the deadly phase of the disease. The incubation period has been observed to vary from a day to over a month.

Inhalation anthrax is considered to be nearly 100 per cent fatal. By the time symptoms appear, it is often too late for antibiotic treatment.

In an interview earlier this month, Dr. Luciana L. Borio, who is a fellow at the Johns Hopkins Center for Civilian Biodefense Studies, said anthrax is a fearsome disease in part because it is hard to diagnose.

“It’s very difficult to detect,” she said. “Someone can have bacteremia (bacteria in the blood) but then you have to do further tests.”

Gastrointestinal anthrax, the third form of the disease, is rare.

All forms of anthrax, however, are rarely transmitted from person to person.

—Staff writer Jonathan H. Esensten can be reached at esensten@fas.harvard.edu.