Dr. David Walker, Chief of Pathology at the University of Texas in Galveston and a member of the visiting team, interviewed Dr. Abramova regarding her autopsy findings. Remarkably, Dr. Abramova and a few of her colleagues had hidden some of their personal notes, records from the autopsies they performed, microscopic slides from organs they examined, and even tissue samples preserved in formaldehyde. When Dr. Walker and others examined all of this material, it became clear that the epidemic was due to inhalation anthrax, not from eating contaminated meat. Thus, in 1992, for the first time, the outside world had proof that the epidemic was due to inhalation anthrax. The significance of this fact is that an epidemic of inhalation anthrax can only occur by inhalation of anthrax spores that were produced in an aerosol form.

Equally remarkable was the detective work done by the members of the team who were trying to identify the source of the inhalation anthrax epidemic. They used a variety of resources:

• Old street maps (the name of the city of Sverdlovsk has been changed to Ekaterinburg)
• Satellite photos of Sverdlovsk
• Weather reports
• Information on the whereabouts of all the victims

From all of this, the investigators pieced together a convincing and chilling reconstruction of what actually happened in Sverdlovsk early in April of 1979.

Here's what they learned. All of the deaths occurred in individuals who lived or worked in a narrow corridor south of military compound #19. From interviews, it was determined that the earliest exposure to the anthrax was on Apr. 2, 1979. Weather reports indicated that on Apr. 2 the wind was blowing from north to south, almost all of the day. Records of livestock deaths around Sverdlovsk showed that six towns reported livestock deaths due to anthrax after Apr. 2, 1979. All six towns were in a narrow corridor south of the city.

The scientific evidence was overwhelming! The outbreak of anthrax in the citizens of Sverdlovsk and the livestock south of the city was due to the wind-borne spread of an aerosol of anthrax spores. The source of the spores was military compound #19 and the escape of spores occurred on Apr. 2, 1979.

The Aftermath

In 1992, Russian president Boris Yeltsin was quoted as saying that the cause of the anthrax accident was "military developments" at compound #19. Thus, although he admitted that the anthrax came from an accident on the military compound, the Russian government released no other information. Theories on the nature of the accident include an explosion in a biological weapons factory on the military compound or workers at the factory forgetting to replace an exhaust system filter. To date, the exact nature of the accident and all of its ramifications, including the total number of victims, have not been disclosed.

However, we have still learned a number of important facts about anthrax as a result of this tragedy. For example, the incubation period (the time from exposure of people to the spores to the development of symptoms) ranged from one day to six weeks. The Sverdlovsk outbreak has also demonstrated some of the strengths and weaknesses of aerosolized anthrax as a biological weapon.

Strengths as a biological weapon include:

• A small amount of anthrax can kill many individuals.
• The spores can travel a significant distance. In Russia, they killed animals more than 30 miles away.

Weaknesses as a biological weapon include:

• The effectiveness of aerosolized anthrax will depend on such atmospheric conditions as wind speed and direction. For example, if the wind had been blowing north, toward the center of the city, many more individuals would have been infected.



• While 5,000 people who lived on the compound and 70,000 who lived south of the compound could have been infected, only about 100 died of the infection, even with this presumably weapons-grade anthrax.



• Since the deaths occurred over weeks, once anthrax is detected, there probably will be time to treat the majority of people exposed. A number of antibiotics are available that can be used to prevent the disease after exposure, or to treat the disease if infection occurs. There is a vaccine available to prevent anthrax, but it is not available to the general public yet.

Another significant consequence of the Sverdlovsk accident is that it led the U.S. Department of Defense to initiate intense research on the use of anthrax as a biological weapon. In addition, the U.S. Centers for Disease Control and Prevention (CDC) have been working with state and local health authorities to prepare for a bioterrorist attack using Anthrax (see CDC Emergency Preparedness and Response website for details). Nevertheless, most of the knowledge we have about anthrax as a biological weapon was generated as a result of the outbreak that began in Sverdlovsk, Russia, on Apr. 2, 1979. We could have learned more, however, if the Russians had been candid about the accident from the beginning. In the words of the investigators and the heroic Russian pathologists: "The tragedy of these deaths is compounded by the conditions of secrecy that have impeded elucidation of many facts that potentially would be useful in the future diagnosis and treatment of inhalation anthrax."

For additional information about Anthrax, please read Dr. Fishbein's Doctor's View, Anthrax, Then and Now.

Acknowledgements

The information in this article comes from a lecture by Dr. David H. Walker at a specialty conference on infectious disease pathology presented at the United States and Canadian Academy of Pathology meeting held on Mar. 16, 1994, and from two publications in scientific journals:

Abramova FA et al. Pathology of inhalational anthrax in 42 cases from the Sverdlovsk outbreak of 1979. Proceedings of the National Academy of Science, Volume 90, pages 2291-2294, March, 1993.

Meselson M et al. The Sverdlovsk anthrax outbreak of 1979. Science, Volume 266, pages 1202-1208, Nov. 18, 1994.