Vol. II, No. 2: 2. Focus On: Anthrax, Separating Facts from Fiction

With anthrax becoming a daily dose of national news, there's increasingly widespread concern about the disease. Fortunately, there's also a lot of good information being disseminated, including the early release of "Recognition and Management of Anthrax -- An Update," by Morton N. Swartz, M.D., of the Department of Medicine at Massachusetts General, the article mentioned in the inset above that will be appearing in The New England Journal of Medicine later this month. But in addition to the solid information -- both for clinicians and laypeople -- there's also an increasing amount speculation and rumor, as well. In an effort to contribute to the facts, then, DownStreet undertook a little research to help separate the facts from the rest.

Types of anthrax
Like many more common and less serious infections, anthrax is a bacterial infection. From the news, most of us are now familiar with the difference between the more serious 'inhalation' anthrax and the 'cutaneous' [skin] form of anthrax. But at least some people seem to be under the impression that they are caused by different types of anthrax bacteria. In fact, they are not.

There is also a third, much more rare and highly morbid form of anthrax, a 'gastrointestinal' variety, as well. But all three are caused by one and the same bacteria -- Bacillus anthracis. According to Dr. Swartz, anthrax "is one of the most molecularly monomorphic bacteria that is known." In other words, all anthrax bacteria show an extremely high consistency in their molecular structure. As a result, Swartz says, "it has been possible to separate all known strains into five categories," which have some correlation with their geographic origins.

The differences, then, have to do with how one is exposed to B. anthracis, as is suggested by the names given to the different types. According to Harrison's Principles of Internal Medicine [15th Ed.], exposure to anthrax is possible by a variety of mechanisms, including "contact with infected animals or contaminated animal products, insect bites, ingestion, or inhalation," as well as the "aerosolized spores [used] in biological warfare or bioterrorism." Cutaneous or skin anthrax follows exposure by direct contact, much like any 'contact dermatitis'. The majority of cutaneous anthrax cases -- which account for 95% of all naturally occurring cases -- arise during the processing of infected animals, e.g., while skinning, butchering, or dissecting them, or, though less often, from bites from contaminated or infected flies. Gastrointestinal anthrax is much more rare, and follows the ingestion of meat from an animal infected with anthrax, most often because it is eaten poorly cooked.

Human anthrax cases are are also classified as either agricultural or industrial, depending upon the source of exposure. Thus, inhalation anthrax is also known as "woolsorters' disease," from its once-common association with that trade, where wool was often processed in facilities without adequate ventilation. As its name implies, inhalation anthrax is caused by breathing in a significant number of anthrax spores. The median number of spores for lethal exposure in inhalation anthrax, estimated from primate studies, is between 2,500 and 55,000. Ordinarily, this high threshold would have accounted for the fact that inhalation anthrax was more rare. But what Swartz refers to as the "weaponizing" of anthrax has introduced a new element into the anthrax equation.

Like many bacteria, in its natural state, B. anthracis has a tendency to clump or bind together, in part because of the inherent electrostatic charge associated with most organisms. But in the process of preparing anthrax as a biological agent for use in warfare, the bacteria is both finely milled and rendered "electrostatically neutral." As a result, many more spores are able to become airborne.

Prevalence of anthrax
According to Harrison's, "Anthrax occurs worldwide and is most prevalent among domestic herbivores (including cattle, sheep, horses, and goats) and wild herbivores. Grazing animals become infected when they forage for food in areas contaminated with spores."

Humans are more resistant to anthrax than these grazing animals. Harrison's places "the estimated number of human cases worldwide [at] 20,000 to 100,000 per year," most of which are the cutaneous or skin form. Most of these cases arise in underdeveloped countries. For example, in Zimbabwe, site of the largest outbreak in recent times, between 1978 and the early 1980s there were "more than 9700 cases." Harrison's attributes that outbreak to the "disruption of the veterinary and medical infrastructure and cessation of veterinary anthrax vaccination programs."

In contrast, here in the U.S., there had not been a case of inhalation anthrax for more than twenty years. Early on in the last century, the U.S. saw roughly 127 cases each year. But both improvements in working conditions and the fact that many fewer workers in the U.S. are now employed in trades that had been traditionally associated with inhalation anthrax had, at least until recently, made it a rarity in this country. As of November 2nd, the CDC had identified a total of 22 cases of anthrax in the U.S. since the recent outbreak, 17 confirmed cases and 5 suspected cases. The following table shows the breakdown for these cases.

Summary of Local, State, and Federal Confirmed Human Cases and Exposures

Case Status	Florida	New York City	New Jersey	Washington, DC	Total
Confirmed	2	5	5	5	17
Cutaneous	0	4	3	0
Inhalational	2	1	2	5

Suspect	0	3	2	0	5
Cutaneous	0	3	2	0
Inhalational	0	0	0	0

Total Cases					22
Source: "Anthrax telebriefing," Centers for Disease Control, CDC Update, Nov. 2, 2001 http://www.bt.cdc.gov/DocumentsApp/Anthrax/11022001/pm.asp

Of considerably greater concern than the outbreak in Zimbabwe, despite its massive proportions, was the largest known outbreak of inhalational anthrax around the same time. In 1979, at least 66 people in Sverdlovsk died after an accidental release of anthrax from a nearby biological weapons research facility. The Soviet cases were initially reported as both cutaneous and gastrointestinal anthrax, but the inhalation mechanism was later confirmed upon careful study of epidemiological data and autopsy results.

But the Soviet Union has not been alone in its experimentation with anthrax in biological warfare. According to a 1997 article which appeared in the Journal of the American Medical Association -- entitled "Iraq’s biological weapons: the past as future?" -- Iraq had admitted after the Gulf War to both producing anthrax and deploying it by missiles. The experimentation and research employed in the manufacture of anthrax as a biological warfare agent includes the milling and electrostatic neutralization mentioned earlier. But the experimentation doesn't end there.

Much of the experimentation with biological agents for use in warfare is centered on genetic engineering. Using methods of recombinant technology, more research facilities than one would care to imagine have been working on developing strains of anthrax and other bacterial and viral agents that would be more resistant to conventional methods of treatment, including the current antibiotics known to be effective. In fact, the U.S. government, after deciding that it could legally proceed despite existing international prohibitions, recently renewed its own efforts at developing precisely this kind of genetically engineered anthrax. [See this month's Straw Poll in Politics and Government for more information.]

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Summary of Local, State, and Federal Confirmed Human Cases and Exposures

Confirmed

Cutaneous

Inhalational

Cutaneous

Inhalational

Total Cases