The following questions and answers were compiled from information available from the Center for Civilian Biodefense Studies at the Johns Hopkins University and from Chest Journal, published by the American College of Chest Physicians.
Bacillus anthracis derives from the Greek word for coal, anthrakis, because the disease causes black, coal-like skin lesions.
How is anthrax contracted?
Naturally occurring anthrax is a disease acquired from anthrax-infected animals or anthrax-contaminated animal products. The disease most commonly occurs in plant-eating animals, which are infected by ingesting spores from the soil. During a 1945 outbreak in Iran, 1 million sheep died. Though animal vaccination programs have greatly reduced animal deaths, anthrax spores continue to be documented in soil samples throughout the world.
What types of anthrax affect humans?
There are three: cutaneous (skin), gastrointestinal and inhalational.
Historically, wool sorters at industrial mills were at highest risk, but today anthrax is rare. Only 18 inhalational cases were reported in the United States from 1900 to 1978, with the majority occurring in special-risk groups, including goat hair mill or goatskin workers and wool or tannery workers. Two of the 18 cases were laboratory associated.
Cutaneous anthrax is the most common naturally occurring form, with an estimated 2,000 cases reported annually throughout the world. Disease typically follows exposure to infected animals. In the United States, 224 cases of cutaneous anthrax were reported between 1944 and 1994.
The largest reported epidemic occurred in Zimbabwe between 1979 and 1985, when more than 10,000 human cases were reported, nearly all of them cutaneous.
Gastrointestinal anthrax is rare, but outbreaks have been reported in Africa and Asia, usually caused by eating contaminated meat that hadn't been sufficiently cooked.
Until the recent Florida cases, no inhalational anthrax had been reported in the United States since 1978, making even a single case a cause for alarm today.
What is the incubation period?
Exposure to airborne anthrax spores could cause symptoms within two days.
However, illness could also develop as late as six to eight weeks after exposure. One case in Sverdlovsk, Russia, developed 46 days after exposure.
How and when did that exposure occur?
In 1979, anthrax spores were accidentally released into the air from a military microbiology facility in Sverdlovsk (now Ekaterinburg), resulting in at least 79 cases of infection and 68 deaths.
How can the release of anthrax as a biological weapon be detected?