Anthrax as a Biological Weapon: Medical and Public Health Management

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Anthrax as a Biological Weapon: Medical and Public Health Management

Journal article

By: Thomas V. Inglesby

Date: May 12, 1999

Source: Thomas V. Inglesby, et. al. "Anthrax as a Biological Weapon: Medical and Public Health Management." Journal of the American Medical Association. (1999): 281, 1735-1745.

About the Author: Thomas V. Inglesby is a physician and Chief Operations Officer of the Center for Biosecurity at the University of Pittsburgh Medical Center in Pittsburgh, Pennsylvania, where he also serves as an associate professor of medicine and adjunct professor of public health.

INTRODUCTION

Anthrax is a pulmonary disease caused by the bacterium Bacillus anthracis. While the disease has gained recent prominence since the deliberate spread of the bacterium in the United States in the autumn of 2001, anthrax has been present for millennia.

The description of the sooty "morain" in the book of Exodus is reminiscent of anthrax, and the disease is probably the "burning wind of plague" in Homer's Iliad. The mass death of horses and cattle (the primary targets of anthrax infection, along with sheep) during the Eurasian campaign of the Huns in 80 CE was also likely due to anthrax.

Accompanying the antiquity of anthrax is the exploitation of the disease as a weapon. Hundreds of years ago, diseased bodies were dumped into wells to poison the enemy's drinking water supply, or were launched over the barricading walls of the fortified cities of the enemy. In modern times, the weaponization of anthrax was a research priority during both world wars. Indeed, during World War II (1939–1945), Britain produced five million anthrax cakes at the Porton Down facility, intended for air-dropping over Germany to infect the food supply.

Human anthrax can occur when the bacterium enters the body via a cut, the ingestion of contaminated food or water, and, most in its most lethal form, when inhaled.

The inhalation form of anthrax typically involves a metabolically dormant form of the organism known as a spore. The spore is designed to protect the genetic material of the bacterium during hibernation during times when nutrients are scare or conditions are harsh. When conditions are better, such as when the spore arrives in the lungs, the spore resuscitates and the bacterium resumes normal growth and division. The anthrax spore is tiny and so can be easily inhaled. As well, few spores are needed to cause anthrax disease.

The dangers of an airborne release of anthrax spores are well known, both historically and in contemporary times. British open-air testing of anthrax weapons in 1941 on Gruinard Island in Scotland made the island toxic for humans and animals even to the present day. In 1979, an accidental release of anthrax spores from a bioweapons facility near the Russian city of Sverdlovsk killed sixty-eight people and sickened at least seventy-nine others who were four kilometers downwind of the accident.

Most recently, beginning on September 18, 2001, letters containing anthrax spores were sent through the United States postal system to media outlets and the offices of two U.S. senators. Inhalation of the spores when letters were opened caused the death of five people. As of 2005, the individual or group responsible for the bioterrorist attack has not been identified.

The report "Anthrax as a Biological Weapon: Medical and Public Health Management" was written almost two years before the September 2001 anthrax attacks, and reflects the difficulty in predicting and preventing a bioterrorist attack using anthrax. Nations and groups that are known to have weaponized anthrax are revealed, and scenarios of attacks in urban areas, including estimated casualties, are outlined.

PRIMARY SOURCE

INTRODUCTION

Of the numerous biological agents that may be used as weapons, the Working Group on Civilian Biodefense has identified a limited number of organisms that could cause disease and deaths in sufficient numbers to cripple a city or region. Anthrax is one of the most serious of these diseases.

High hopes were once vested in the Biological Weapons and Toxins Convention, which prohibited offensive biological weapons research or production and was signed by most countries. However, Iraq and the former Soviet Union, both signatories of the convention, have subsequently acknowledged having offensive biowarfare programs; a number of other countries are believed to have such programs, as have some autonomous terrorist groups. 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.

Biological agents have seldom been dispersed in aerosol form, the exposure mode most likely to inflict widespread disease. Therefore, historical experience provides little information about the potential impact of a biological attack or the possible efficacy of postattack measures such as vaccination, antibiotic therapy, or quarantine. Policies and strategies must therefore rely on interpretation and extrapolation from an incomplete knowledge base. The Working Group on Civilian Biodefense reviewed the available literature and expertise and developed consensus recommendations for medical and public health measures to be taken following such an attack….

HISTORY OF CURRENT THREAT

For centuries, anthrax has caused disease in animals and, uncommonly, serious illness in humans throughout the world. Research on anthrax as a biological weapon began more than 80 years ago. Today, at least 17 nations are believed to have offensive biological weapons programs; it is uncertain how many are working with anthrax. Iraq has acknowledged producing and weaponizing anthrax.

Most experts concur that the manufacture of a lethal anthrax aerosol is beyond the capacity of individuals or groups without access to advanced biotechnology. However, autonomous groups with substantial funding and contacts may be able to acquire the required materials for a successful attack. One terrorist group, Aum Shinrikyo, responsible for the release of sarin in a Tokyo, Japan, subway station in 1995, dispersed aerosols of anthrax and botulism throughout Tokyo on at least 8 occasions. For unclear reasons, the attacks failed to produce illness.

The accidental aerosolized release of anthrax spores from a military microbiology facility in Sverdlovsk in the former Soviet Union in 1979 resulted in at least 79 cases of anthrax infection and 68 deaths and demonstrated the lethal potential of anthrax aerosols. An anthrax aerosol would be odorless and invisible following release and would have the potential to travel many kilometers before disseminating. Evidence suggests that following an outdoor aerosol release, persons indoors could be exposed to a similar threat as those outdoors.

In 1970, a World Health Organization (WHO) expert committee estimated that casualties following the theoretical aircraft release of 50 kg of anthrax over a developed urban population of 5 million would be 250,000, 100,000 of whom would be expected to die without treatment. A 1993 report by the US Congressional Office of Technology Assessment estimated that between 130,000 and 3 million deaths could follow the aerosolized release of 100 kg of anthrax spores upwind of the Washington, DC, area—lethality matching or exceeding that of a hydrogen bomb. An economic model developed by the Centers for Disease Control and Prevention (CDC) suggested a cost of $26.2 billion per 100,000 persons exposed….

SIGNIFICANCE

"Anthrax as a Biological Weapon: Medical and Public Health Management" provided recommendations that were utilized during the 2001 anthrax attacks by public health officials, including recognizing and treating anthrax disease in patients, decontaminating an environment after contamination with anthrax, and preventing the disease in those exposed to anthrax. Inglesby and his colleagues, then at the Johns Hopkins Center for Civilian Biodefense Strategies in Baltimore, Maryland, revised the article after the 2001 anthrax attacks to include new information, including diagnostic clues, updated vaccination recommendations, judgments about environmental surveillance and decontamination, future research, and newer antibiotic treatments.

Anthrax infections are difficult to treat because the initial symptoms are similar to other, less serious, infections such as the flu. By the time the true nature of the threat is realized, the infection is well established and may be too advanced to treat.

Three components of Bacillus anthracis cause anthrax. A protective capsule that surrounds the bacterium blunts recognition of the invading bacterium by the body's immune system and lessens the antibacterial action of antibodies and immune cells that do respond to the infection. This protection early in infection can allow the organism to grow to large numbers. The capsule also contains a so-called protective antigen that allows the bacterium to protrude through membrane of host cells, and burrow away from the hosts' immune defenses. Finally, a component called edema factor disables a host molecule called calmodulin, which is used to regulate many chemical reactions in the body. In anthrax, edema factor causes fluid to accumulate at the site of infection.

As the infection proceeds, toxins produced by the bacteria enter the bloodstream and circulate throughout the body. The resulting cell death and tissue destruction can be lethal.

A vaccine to anthrax does exist, but the possibility of serious side effects has restricted its general use. As of 2005, the vaccine is restricted to those deemed to be at high risk (soldiers, workers in meat processing plants, anthrax research scientists). Among the candidate targets of a safer vaccine are the edema factor and the protective antigen of the bacterium's capsule. The latter is crucial for the entry of the bacterium into host cells. Its compromise would thwart the ability of the invading bacteria to hide inside host cells, and so they would be more effectively killed by the immune reaction and applied antibiotics.