Thinking the unthinkable: possible bioterrorism scenarios

October 2001

Usually at this time of year, this column would be devoted to a recapitulation of last year’s influenza experience, what might be expected during the coming season, and the usual exhortations about influenza vaccination. Maybe next month, but not now. It’s a different country and a different world than it was last month, and some of the differences have already impacted the infectious disease community, and these will likely continue and increase.

In addition to our own individual reactions to the tragic events of that day, one of the central truths that has emerged is that we, as individuals and as a society, feel much less secure these days than we did a month ago; our previous confidence in personal and societal security has been shattered beyond easy repair.

It is not at all surprising, therefore, that the possibility of biological/chemical terrorist attacks looms large in our perceptions about future attacks. As well it should! Any terrorist group or collection of “cells” smart enough, disciplined enough, bank-rolled enough, and trained enough to pull off the dramatic events of Sept. 11 could surely put together an operation to expose some segment of the population in this country to a biological agent or a toxin that would result in an identifiable bioterrorist “event.” In many possible scenarios, especially those dealing with biological agents, the exposure would likely be a silent event, recognized only in retrospect after multiple cases of ________ (fill in the blank) had been diagnosed and one or more common factors identified.

Such an event would, of course, lack the dramatic and chilling effects of unimaginable spectacles such as fully fueled aircraft flying at full throttle into 100-story buildings and resulting in huge fireballs. To the extent that a terrorist mind wants to create such a devastating visual impact, that would favor the use of high explosives in some kind of delivery system. A biological event, however, even a small and limited one, would in my view result in just as much fear and terror for personal safety, largely because of the stealthy and unrecognized nature of the exposure itself. It needn’t be a huge exposure, involving perhaps 75,000 people at an NFL football game. A hotel, large store, shopping mall, convention center or concert hall would probably do just fine! The magnitude of the body count is really not the issue.

Hysteria

Thus, it is not surprising that there has been a steady, even an increasing level of publicity about the possibility of bioterrorism in both public and professional media. To the extent that this publicity makes us all, physicians included, more concerned, more aware, and more alert to unusual or suspicious behaviors, it is all to the good. It would not take much more publicity and public commentary, however, to bring about near or actual hysteria, and the irrational behavior that inevitably results. In fact, we may be seeing this in some quarters already.

There are, for example, widespread media reports of “runs” on ciprofloxacin, recommended for the treatment of anthrax; many folks are acquiring a full 60-day supply. This practice is permitted and even encouraged by a number of physicians. If an anthrax exposure were announced by the perpetrators as it was happening – sure, I would take some ciprofloxacin, too, and so would my exposed family members. Such a scenario is quite unrealistic, however, and in all likelihood, an exposure will not be recognized until after cases have been diagnosed. We simply don’t know how effective ciprofloxacin will be, if at all, in a given patient once symptoms have become apparent.

Similarly, there is renewed interest in several vaccines that previously were of little or no interest to the civilian community. Anthrax vaccine is one example; there is none to be had. Smallpox vaccine is another; there is none to be had — at least at present. Some may become available in late 2002 — the first released from an initial contract with Acambis PLC, a British biotech company, for 40 million doses. Personal nonphysician friends ask me if I know where any doses of smallpox vaccine can be had; “we know it’s out there,” they say.

It’s not easy

Working in our favor is the fact that an effective exposure to a biological agent is quite difficult to pull off. In addition to the scientific challenges of making sufficiently large quantities of the agent and maintaining it in an infective state, there are the engineering challenges of delivering it to a group of people in an infective concentration. For closed exposures, that means access to an air handling system, presumably maintained in a secure fashion. For open-air exposures, the odds are even more daunting. Most biological agents are fragile, quickly inactivated by ultraviolet light, diluted well below their ID₅₀, or simply blown away by the breeze. None of this is to suggest such events will not occur — only that the odds are long. Furthermore, that only covers air-borne exposures; water-borne or foodborne biological agents are quite another matter, requiring a different set of challenges and approaches to control. Recall, however, that there has been at least one documented instance of deliberate large-scale foodborne contamination in the United States, that being Salmonella contamination of multiple salad bars in Dalles, Ore., that involved 750 persons.

Take-home message

What’s the message to infectious disease physicians? Simply this: be informed, and be alert; you may need to think the unthinkable. CDC’s “A” list of the biggest biological threats includes inhalation anthrax, smallpox, pneumonic plague, botulinum toxin, tularemia, filoviruses such as Ebola, and arenaviruses such as Lassa. Of these, anthrax and smallpox have garnered the greatest concerns.

Be aware of the resources to help should you need them. These have recently been summarized by the IDSA and include:

• The Centers for Disease Control at www.bt.cdc.gov.
• Johns Hopkins Center for Civilian Biodefense Studies at www.hopkins-biodefense.org.
• U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) at www.usamriid.army.mil.
• Finally, IDSA’s own Web site at www.idsociety.org in the “Members Only” section.

Readers who are EIS alumni may recall that, thanks to the great foresight of Alex Langmuir, the EIS program was established 50 years ago this year, owing in very large part to the threat of biological warfare. We are no longer talking about “warfare,” at least in the 1951 sense of that term. Now 50 years later, the threat has again emerged, not on the battlefield, but right here at home, far more subtle, but just as fearful.

Be informed and be alert. Pray that you will not need to think the unthinkable.