Shedding some light on anthrax


Primer: Answers are provided to questions about a disease gaining more attention from a nervous American public.

October 13, 2001

Anthrax has been identified as a disease in animals and humans for centuries, and its use as a biological weapon has been studied for 80 years. Still, most people know little about it.

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.

Where does the name anthrax come from?

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?

The first evidence of a clandestine release of anthrax as a biological weapon most likely will be patients seeking medical treatment for symptoms of inhalational anthrax.

Currently, there are no effective atmospheric warning systems to detect an aerosol cloud of anthrax spores.

Do many nations or groups have offensive biological weapons programs?

At least 17 countries are believed to have offensive biological weapons programs, though it is uncertain how many are working with anthrax. Iraq has acknowledged producing anthrax in weapon form. Experts generally agree that the manufacture of a lethal anthrax aerosol is beyond the capacity of individuals or groups without access to advanced biotechnology.

However, groups with substantial funding and contacts might be able to acquire the required materials for a successful attack.

One terrorist group, Aum Shinrikyo, responsible for the release of the toxin sarin in a Tokyo, Japan, subway station in 1995, dispersed aerosols of anthrax and botulism throughout Tokyo on at least eight occasions. For unclear reasons, the attacks failed to produce illness.

How dangerous is anthrax?

Its use as a weapon could be serious. Once it was hoped that the Biological Weapons and Toxins Convention, which prohibited offensive biological weapons research or production and was signed by most countries, would be a deterrent.

However, Iraq and the former Soviet Union, both signatories, later acknowledged having offensive biowarfare programs. The possibility of a terrorist attack using bioweapons would be especially difficult to predict, detect or prevent, and thus it is among the most feared terrorist scenarios.

In 1970, a World Health Organization expert committee estimated that casualties after the theoretical aircraft release of 50 kilograms of anthrax over a developed urban population of 5 million would be 250,000, with 100,000 victims expected to die.

A 1993 report by the U.S. Congressional Office of Technology Assessment estimated that between 130,000 and 3 million deaths could follow the aerosolized release of 100 kilograms of anthrax spores upwind of Washington, D.C., a degree of lethality matching or exceeding that of a hydrogen bomb.

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