about Epidemiology & the department

Epidemiology academic information

Epidemiology faculty

Epidemilogy resources

sites of interest to Epidemiology professionals

Last Updated

11 Dec 2002

Source: The Weekly Standard 7(32), April 29, 2002.

Remember Anthrax?

Despite the evidence, the FBI won't let go of its "lone American" theory.

by David Tell

1) OVER THE PAST SIX MONTHS, have federal authorities altered their working theory of last fall's anthrax murders?

No, not much. On November 9 last year, even before the anthrax outbreak's fifth and final fatality had been recorded (case 23), the FBI called a press conference to unveil its "linguistic and behavioral assessment" of "the person" purportedly responsible. It was "highly probable, bordering on certainty," the Bureau announced, that a single "adult male" had prepared and mailed all the contaminated letters at issue. This man "probably has a scientific background," "may work in a laboratory," and is familiar with the area around Trenton, New Jersey -- where the envelopes were postmarked. He suffers a pronounced psycho-social deformity: "He lacks the personal skills necessary to confront others" and "if he is involved in a personal relationship, it will likely be of a self-serving nature." Moreover, crucially, the suspect appears to be an American. "We're certainly looking in that direction right now, as far as someone being domestic," said James R. Fitzgerald, head of the FBI's Behavioral Analysis Unit.

By the end of November, after an unopened anthrax letter addressed to Sen. Patrick Leahy was found in sequestered congressional mail, investigators were telling reporters on background that they might well be dealing with someone who has a particular animus against Democrats. His politics aside, the man's citizenship, at least, achieved a measure of official status by mid-December, when homeland security chief Tom Ridge, seconded by White House spokesman Ari Fleischer, acknowledged that where once "some of us" had been "thinking more in terms of foreign sources," now "a lot of the information and a lot of the things they've been able to detect from the investigation and follow-up leads ... they're looking more inward to a domestic source."

On January 29, confirming its impression of the domestic source's professional profile, the FBI sent a letter to all 40,000 members of the American Society for Microbiology which informed those scientists that it is "likely one or more of you know this individual." On February 26, the New York Times reported that what had once been a "pretty tight list" of investigative subjects in the world of microbiology--perhaps 100 U.S. laboratories and their employees--had been whittled down to a group of 35 to 50 "researchers or technicians" and then narrowed still further to maybe 18 or 20 people with the means and potential motive to send deadly bacteria through the mail.

Two weeks ago, numerous published reports suggested that the FBI has recently lost a fair bit of confidence in the focus of its investigation; the universe of potential suspects, "law enforcement sources" now say, actually numbers in the "thousands." Nevertheless, the government continues to expect that the one guilty man among those thousands will turn out to be an American biological researcher of some kind.

2) What makes them think he's an American?

The FBI has declined to explain its profiling rationale in any detail, and Tom Ridge's references to "follow-up leads" and other "things they've been able to detect" remain ambiguous. But a woman named Barbara Hatch Rosenberg, whom the Bureau has consulted, and whose analysis of the case mirrors its own in certain key respects, has tirelessly publicized the results of some ambitious amateur detective work.

Rosenberg is a research professor of environmental science at the State University of New York in Purchase. She also directs a working group on biological weapons verification for the Federation of American Scientists. And in a running "commentary" she has maintained on the federation's Internet site (, Rosenberg argues that "multiple, blatant clues" left "seemingly on purpose" all make clear that "the perpetrator of the anthrax attacks is American." First off, the letters in which his spores were wrapped warned recipients to take an antibiotic, establishing that he "did not aim to kill" -- as would be the goal of a genuine al Qaeda operative -- but sought simply "to create public fear." Furthermore, according to Rosenberg, the spores themselves were prepared following the "optimal U.S. process" secretly perfected decades ago by Army biowarfare specialists at Ft. Detrick in Frederick, Maryland. "The anthrax in the letters," Rosenberg flatly asserts, "was either made and weaponized in recent years in a U.S. government or contractor lab for biodefense purposes, or by the perpetrator on his own." Either way, last fall's bacteriological terrorism against the United States was undoubtedly "an inside job."

Given the understandably intense jealousy with which federal investigators have guarded whatever hard evidence they themselves have accumulated in the case, media attempts to substantiate the FBI's conviction that a deranged current or former government scientist is behind the anthrax attacks have necessarily been based almost exclusively on the speculation of outside "experts." And no such expert has been more widely or respectfully cited, at the highest reaches of American journalism, than Barbara Hatch Rosenberg. After all, notes the New Yorker, Rosenberg is "not chopped liver." She is a "veteran molecular biologist" with a long-term professional interest in biological weapons -- and "deeply concerned hazel eyes."

Which may be true. But it is also true that this veteran molecular biologist's sensational pronouncements betray a surprisingly uncertain grasp of contemporary genetic research and clinical protocols concerning Bacillus anthracis. And a surprisingly limited familiarity with anthrax-related military and civil-defense projects around the world. And a surprisingly unscientific, even Oliver Stone-scale, incaution about the "facts" at her disposal.

Rosenberg claims the FBI has known the anthrax mailer's precise identity for months already, but has deliberately avoided arresting him -- indeed, may never arrest him -- because he "knows too much" that the United States "isn't very anxious to publicize." Specifically, according to an account the hazel-eyed professor offered on BBC Two's flagship "Newsnight" telecast March 14, the suspect is a former federal bioweapons scientist now doing contract work for the CIA. Last fall, you see, the man's Langley masters supposedly decided they'd like to field-test what would happen if billions of lethal anthrax spores were sent through the regular mail, and "it was left to him to decide exactly how to carry it out." The loosely supervised madman then used his assignment to launch an attack on the media and Senate "for his own motives." And, this truth being obviously too hot to handle, the FBI is now trying very hard not to discover it.

What if "some kind of deal is made that the perpetrator just disappears from view," Rosenberg worries aloud? She appears already to have taken proactive steps to thwart such a conspiracy. Over the past several months, using language lifted almost verbatim from Rosenberg's website, ABC News and the Washington Times have both fingered the same unnamed "top scientist" as the FBI's only (never-to-be-revealed) anthrax suspect. Except that the poor man turns out to be a former Ohio laboratory technician who has never done bacteriological research of any kind -- and whose unfortunate history of alcoholism has lately reduced him to working in a Milwaukee-area bowling alley. Which bowling alley has no known ties to the CIA's Directorate of Operations.

Barbara Hatch Rosenberg's theory is crackpot.

3) Well, wait a minute. Wasn't the anthrax powder mailed last fall chemically identical to stuff produced in classified U.S. labs?

That's far from clear, and even if it were clear it probably wouldn't help solve these crimes.

In order to produce inhalation anthrax, bacterial spore-particles must be small enough -- no more than a couple or three microns wide -- to reach a victim's lower respiratory mucosa. And for decades, until very recently, scientists believed that the mechanical milling required to produce such fine dust artificially would also produce a charge of static electricity sufficient to bind anthrax spores together into oversized, harmless clumps. To prevent this from happening -- to keep the spores separate, "floaty," and therefore deadly -- bioweapons specialists in the United States and elsewhere went to considerable lengths to identify a chemical additive that would, like throwing a sheet of Bounce into your clothes dryer, remove the static. It has been widely reported, but never confirmed, that American scientists eventually settled on silica. It has been just as widely reported, and more or less confirmed, that the Soviet and Iraqi biowarfare programs each at some point used a substance called bentonite, instead.

The Armed Forces Institute of Pathology has performed energy dispersive X-ray spectroscopy on anthrax powder recovered from at least two of last fall's letters and has apparently discovered trace amounts of silica, but no sign of aluminum, an element basic to the best-known and most common form of bentonite (montmorillonite).  Based on this result, government investigators have concluded, according to the Washington Post, that "it is unlikely that the spores were originally produced in the former Soviet Union or Iraq." On the same basis, and getting similarly ahead of herself, Barbara Hatch Rosenberg has decided the spores were prepared by a rogue or sanctioned U.S. laboratory worker.

But the fundamental chemistry involved here cannot sustain such certainty. Silica, or silicon dioxide, is simple quartz or sand, the most abundant solid material on earth. "Bentonite" is the generic term for a class of natural or processed clays derived from volcanic ash, all of which are themselves mineral compounds of silica -- and not all of which necessarily contain aluminum. In other words: Trace amounts of silica in an anthrax powder are consistent with the presence of bentonite. And the absence of aluminum from that powder is not enough to exculpate any foreign germ-warfare factory thought to have used bentonite in the past.

The FBI and Rosenberg seem also to have ignored what has been standard practice in U.S. biodefense, medical, and veterinary laboratories for most of the past thirty years: Work with virulent strains of anthracis in dried-spore, aerosolized form is virtually unheard of. Pentagon production of weapons-ready -- and presumably silicate -- anthrax powder was abandoned during the first Nixon administration. The U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) at Fort Detrick, for example, doesn't even own the requisite technology to manufacture dry aerosols; USAMRIID scientists, like their civilian counterparts, use only "wet" anthrax -- which has usually been genetically altered or irradiated to render it non-toxic.

There is one known exception to this rule. Four months ago the Army's Dugway Proving Ground in Nevada confirmed that in recent years it has conducted occasional, limited experiments with fully pathogenic anthrax powders -- reportedly to test prophylactic measures against a frightening, vaccine-resistant strain of the bacterium thought to have been cooked up by Russian geneticists during the early 1990s. Here's the thing, though: The Army is mum on the question, but there is no reason to think that Dugway's virulent aerosols (every speck of them fully accounted for, laboratory officials insist) were prepared with silica, according to the rumored 1960s recipe. The science of environmental engineering, which hardly existed in the 1960s, has lately revealed a great deal of new information about the dispersal patterns of anthracis and other airborne microbes. As a consequence, old assumptions about the effect of electricity on the aerosolization of bacterial pathogens -- like those from a just-opened letter -- have been revised: Lethal quantities of lethally small anthracis particles can and do spread over a large area, on normal indoor air currents and in very little time, whether or not they have been treated with an anti-static compound.

So whoever was responsible for last fall's bioterrorism wouldn't have needed to add silica to his anthrax powder at all. But he -- or she, or they -- might have had use for it while manufacturing that powder to begin with. Before they were kicked out of Iraq for good, U.N. weapons inspectors concluded that Saddam's military biologists were no longer relying on mechanical milling machines to render dried-out paste-colonies of anthracis bacteria into fine dust, but had instead refined a spray drying technique that produced the dust in a single step. And the suspected key ingredient in this Iraqi innovation, interestingly enough: pharmaceutical-grade silica, a common industrial drying agent.

4) But last fall's anthrax was milled mechanically, so it can't have come from Iraq, right?

We don't know that it was milled, really. Published reports conflict on this point, and those news accounts that do suggest the anthrax was milled invariably attribute the intelligence to federal investigators impressed by the super-granulated quality of the Leahy sample. In fact, evidently concerned that the Leahy letter might thus tend to confirm the Barbara Hatch Rosenberg conspiracy theory at its most rococo (i.e., that someone walked the anthrax straight out of a CIA lab), certain "government sources" have lately begun putting out word that the stuff was actually too good to be American. Two weeks ago, an item in Newsweek described a "secret new analysis" said to be circulating through high-level Washington, according to which analysis the Leahy letter's powder was "ground to a microscopic fineness not achieved by U.S. biological weapons experts." Researchers have found evidence of "intense milling," Newsweek explained: individual, free-floating anthracis spores, something our own government's scientists have "never seen" before.

But that's absurd. Individual, free-floating anthracis spores are what those scientists look at every day. And it's hardly a secret. During a December 15 Centers for Disease Control-sponsored conference on post-exposure prevention of inhalation anthrax -- you can find the transcript on CDC's website -- Dr. Louise Pitt of USAMRIID discussed in considerable detail how her colleagues at Ft. Detrick do their anthracis research. The spores, she said,

"are diluted to the desired concentration in sterile distilled water, water for injection. Our aerosols are extremely well characterized and defined. The particle size of the aerosol has a mass-meeting-aerosol diameter between .8 and 1.4 microns. That means that the aerosols that we are generating are basically single-spore aerosols. There's very, very little clumping of two spores. They are single-spore aerosols."

And remember, Ft. Detrick does not employ a mechanical milling process. Because, as it happens, people like Dr. Pitt have discovered much easier ways to make what our experts persist in calling the Leahy letter's "weapons-grade" anthrax: If they want it in a mist, they dilute the spores in water, as USAMRIID does. And if they want their anthrax dry, in a powder, they run it through what is essentially a very fancy flour sifter, a device commercially available throughout the world. This practice, too, has been specified in the open literature. A "Risk Assessment of Anthrax Threat Letters" published last year by Canada's Defence Research Establishment Suffield (DRES), for instance, was based on a bacterial specimen prepared in the "routine manner." Agar-grown cultures were dried into a "clumpy, undistinguished mess." And the mess was then filtered with a sifter, separating the largest chunks and leaving behind a final powder containing "a high proportion of singular spores."

Under a microscope, of course, singular spores, both milled and unmilled, look exactly the same.

5) What about the fact that last fall's attacks involved the American "Ames" strain of anthrax?

Careful. On October 25, at the height of the crisis, Tom Ridge announced that the bacteria were of "the Ames strain" or "an Ames strain." That same day, however, Dr. Jeffrey Kaplan, director of the CDC, said that anthracis samples taken from letters mailed to Sen. Tom Daschle and the New York Post -- and from the spinal fluid of Florida photo editor Bob Stevens (case 5), the outbreak's first victim -- were consistent with "a number of different strains." Kaplan's deputy, Dr. Julie Gerberding, added a further nuance. The Daschle, Post, and Stevens samples -- "strains," she also called them -- were "indistinguishable."

But if they were indistinguishable, how could they be different "strains"? During a November 14 CDC "telebriefing," Gerberding acknowledged that "it's very important to set the record straight on this issue." And she made a valiant attempt to do so:

"These strains in the various regions of the country that we're dealing with are indistinguishable on the basis of their antibiotic susceptibility as well as their typing using more sophisticated molecular tools, and they have some characteristics in common with several of the naturally acquired strains of anthrax that have been seen in animals in the United States and in the United Kingdom and elsewhere .... But they're not identical."

Got that?

6) What's going on here? Is it Ames or isn't it?

Insofar as any of them feels sure of the answer, none of the scientists now working with the government will state it unambiguously, in part because they are concerned for the security of a massive ongoing investigation. Even were security not a concern, however, the question whether they are dealing with "the Ames strain" would still be a vexed one, for two reasons. First, "strain" is a word that has no fixed, technical meaning: Any set of microbes with closely related genetic characteristics gets called a "strain," but how closely related they must be -- at what level of analysis should a set of microbes be subdivided into "strains" -- is a subjective judgment. Is your second cousin "family" or merely distant kin?

Then there is the peculiar nature of anthrax itself. Anthracis is the world's most molecularly homogeneous bacterial species. As recently as 1995, every laboratory isolate ever tested appeared to be genetically identical, and only three of them had been labeled strains. There was Sterne, named after the South African researcher who developed veterinary medicine's still-standard anthrax vaccine. There was Vollum, originally recovered from livestock in England and a staple of the U.S. bioweapons program in the 1960s. And there was Ames, so dubbed by a USAMRIID scientist in 1981 (for the town in Iowa, though the sample actually originated in Texas). The Sterne strain was sui generis; it didn't cause disease. But no one knew exactly why, and the three strains remained genetically indistinguishable.

In 1996, a group of researchers at a Veterans Administration hospital in North Carolina were the first to announce the detection of meaningful differences in the DNA of various anthrax isolates; anthracis, they thought, was a species encompassing five distinct genetic subgroups. Over the next few years, building on this work, Dr. Paul Keim of Northern Arizona University in Flagstaff examined hundreds of anthrax samples from a collection maintained by Louisiana State University veterinarian Martin Hugh-Jones and further refined the bacterium's phylogeny: He found 89 unique genomes -- strains, if you dare -- in six major families of anthracis. Then, in 1999, Tim Read of the non-profit Institute for Genomic Research in Rockville, Maryland, published a full map of the Ames strain's main chromosome on the Internet -- all the DNA letter-strings for nearly 6,000 genes. Using Read's data, Keim has since located at least 50 places along the anthrax genome where various strains diverge, and he believes he has positively fingerprinted more than 100 such strains in his own ballooning archive of bacteria.

Keim and Read are both heavily involved in the current investigation. Read has completed another full sequence of anthracis DNA, this one taken from Bob Stevens (case 5), last fall's first fatality. Keim has compared that roadmap with Read's previous, Ames-strain diagram. The two samples are said to be a match.

But they can only be a match within the limits of Keim's existing classification system for anthrax. And back in the fall, before they stopped talking to the press so frequently, he and Read were quite candid about what those limits entail. Bacillus anthracis mutates into separate strains at a glacial pace. It takes maybe a million generations before even a single piece of its DNA is altered. And any given isolate of the bacteria finishes only a few hundred of those reproductive cycles during each active life span, while infecting an animal or human host. Then, if it's lucky enough not to be killed by antibiotics or incinerated with its victim's corpse, an anthrax colony hibernates in sporulated form for decades at a time. It is because their opportunities for genetic development have been so few and far between that many of the anthracis strains Paul Keim believes he has identified are separated by just a handful of DNA nucleotides -- out of more than five million in the bacterium's full genome.

Which means, Keim admitted to Science magazine back in November, that many of his putative strains cannot be distinguished from one another outside the margin of error for current DNA sequencing technology: one misread nucleotide in every 100,000 examined. Around the same time, asked by an NPR radio interviewer whether it would be "possible to find out who sent the anthrax, where it came from, [by] doing gene studies of it," Tim Read paused a moment -- and said, "I don't think so."

7) Assuming that it were possible to match last fall's anthrax with the Ames strain, would that mean it had to have come from an American laboratory?

No. The bacterial culture that Army biologist Gregory Knudson called "Ames" in 1981 came from a 14-month-old, 700-pound Beefmaster heifer that had recently died on a ranch in Jim Hogg County, Texas. So far as modern science can determine, an identical form of anthracis continues to widely contaminate the soil in south Texas. In 1997, 16 years after the Jim Hogg case and hundreds of miles to the northwest, Ames is known to have killed at least one goat -- and to have sickened two ranchhands who cut open the poor beast's stomach and poked around inside before storing the carcass in a kitchen freezer. Ames, as the CDC correctly asserts, is a naturally occurring bacterium. Want some? "I'd look for a dead animal," LSU's Martin Hugh-Jones advises. "You could just take some blood from the animal, some tissue, and swab and grow it up on blood agar -- nothing easier .... I'd say first-year college microbiology."

You wouldn't even have to make a trip to Texas. Or be in the United States at all. Very closely related strains of anthrax -- again, within the margin of DNA sequencing error--have been recovered from infected livestock in Argentina, England, South Africa, India, Australia, and China.

8) Really, though: Isn't it more likely that what we're talking about was stolen or cloned from a pre-existing laboratory stock?

Yes, but that doesn't help narrow things down much, either. Barbara Hatch Rosenberg's website lists Canada's DRES and a place called Porton Down in England as the only foreign installations known to keep Ames in their collections. Her list is woefully incomplete. Porton Down alone has openly acknowledged sharing Ames cultures with its associated public health agency, the Centre for Applied Microbiology and Research. And that outfit in turn has acknowledged distributing Ames to an unspecified number of private researchers.

What's more, in March of last year a group of French scientists at the Centre d' tudes du Bouchet published a report on experiments they'd conducted with their own Ames sample. And explained that they'd collaborated on those experiments with a second French laboratory at the University of Paris. And expressed gratitude for shipments of Ames they'd received from a third French laboratory, the Institut Pasteur. And from a fourth French laboratory at the Agence Fran aise de S curit  Sanitaire des Aliments. And from one Dr. Mats Forman of Sweden, too.

The stuff is all over the place. It is almost certainly held in one or more Russian depositories. According to an elaborate forensic analysis sponsored by the National Academy of Sciences in 1998, the accidental 1979 explosion of a Soviet biowarfare factory in what was then Sverdlovsk released no fewer than four separate strains of anthracis into the atmosphere, one of which is now grouped in the same subtype as Ames. At its height in the early 1990s, the Soviet germ-weapons program, Biopreparat, had 2,000 scientists working exclusively on anthrax. Those few of them who remain employed by successor agencies are currently paid $100 per month to maintain custody of laboratory facilities like the one in Obolensk -- which is critically delinquent in its payments for the electricity necessary to keep 3,000 different anthrax isolates, the world's largest collection, safely on ice.

All of which makes penetration of the wobbly Russian biodefense establishment -- by rogue nations or terrorist organizations -- a worrisome and real possibility. Iran, for example, is known to have recruited a number of disgruntled or indigent Russian military biologists. Saddam Hussein, on the other hand, is not known to have bagged any Russians.

But he may not need to. Top Iraqi scientists Nassir Hindawi and Abdul Rahman Thamer first tried to acquire a sample of the Ames strain from Porton Down in 1988. They were turned down, but over the next two years they did manage to purchase an enormous quantity of anthrax-ready biological growth medium from a British commercial supplier. And nine other strains of anthracis from the Institut Pasteur and an American company now located in Manassas, Virginia. And at least two variants of the intensely pathogenic Vollum strain from ... who knows where, and in addition to who knows what else.

In late November, a "microbiologist who has studied Ames" told the Washington Post he thought "the probability that [the Iraqis] don't have the strain is near zero."

9) Surely the FBI has some substantial reason to discount such fears and focus its attention on a domestic suspect?

That could well be, but if so they're keeping it to themselves.

There is purely circumstantial though highly suggestive evidence that might seem to link Iraq with last fall's anthrax terrorism. The U.N.'s former top bioweapons inspector in Iraq, Richard O. Spertzel, has told Congress about reports of a "cryptic September article in a newspaper run by Saddam's son, Uday" which promised that a "virus" would soon attack "the raven," apparently a Baath party curseword for America. Spertzel has also told Congress that Iraq has conducted military exercises simulating the dispersal of anthrax spores from crop-dusting aircraft -- a subject in which both Mohamed Atta and Zacarias Moussaoui, the alleged "twentieth hijacker," are known to have expressed intense interest. Last June, one of Atta's September 11 confederates, Ahmed Ibrahim Al Haznawi, walked into a Fort Lauderdale, Florida, emergency room with a painless but inflamed one-inch black lesion on his lower left leg. In retrospect, Al Haznawi's attending physician, Dr. Christos Tsonas, is convinced that the wound was cutaneous anthrax. The Department of Health and Human Services' top bioterrorism expert agrees, as do two leading researchers at the Johns Hopkins University Center for Civilian Biodefense Strategies.

And so on. The FBI has hardly said a word about why it is inclined to mistrust or make light of such signals. And what little the Bureau has offered about why it prefers to focus instead on possible American suspects isn't especially persuasive, unfortunately.

FBI handwriting experts have somehow determined that the xerox-copied taunts included with last fall's anthrax letters -- "We have this anthrax. You die now. Are you afraid?" -- were written by a native English-speaker, though they note without venturing an explanation that "he" used only block lettering, with slightly larger block letters at the beginning of every noun. Might it also be that "he" wasn't a native English-speaker at all, but rather someone who grew up speaking a language -- like Arabic -- whose alphabet has no upper or lower cases? Someone whose experience with Romance-language script was limited to his temporary residence in, say, the one Western country where nouns are always capitalized? That would be Germany, once home to Mohamed Atta and any number of other al Qaeda operatives. It is not clear whether the FBI has considered this clue.

By contrast, the Bureau and its allied "home-grown terror" theorists have clearly given a great deal of thought -- too much thought -- to the fact that their suspect left no potentially incriminating personal marks on last fall's letters: no fingerprints anywhere on the envelopes or xeroxes, and no saliva on the envelopes' adhesive flaps. To Barbara Hatch Rosenberg, this indicates that the mailer was a spook-like U.S. government insider, someone with "training or experience in covering evidence." Similarly, and for the same reason, the FBI believes Anthrax Man exhibited a notably "organized, rational thought process in furtherance of his criminal behavior." Actually, though, all he exhibited was a bare minimum of human brain function and an animal instinct for self-preservation. Ask yourself: Would you be willing to touch with your bare hands, much less lick with your tongue, an envelope containing two billion spores of the universe's most dangerous bacterium? The question answers itself.

Speaking on background to reporters, FBI officials have repeatedly endorsed Professor Rosenberg's interpretation of the mysterious advisory included with two of the anthrax mailings -- that their recipients should begin taking "penacilin." The misspelling, Rosenberg argues, is a deliberate feint intended to distract investigators from the truth, and the prescription itself is what should lead them back: The reference to penicillin means the perpetrator was an American scientist, knowledgeable about the clinical protocols for treatment of anthrax, and eager to cure those of his fellow citizens whom he was simultaneously making very sick. But it means nothing of the kind, in fact. No true expert, benignly inspired, would nowadays prescribe penicillin for an anthracis infection. Ever since Tim Read published his Ames-strain DNA sequence in 1999, American researchers have understood that the organism's genes encode a beta-lactamase enzyme that neutralizes penicillin. American public health agencies have responded accordingly. CDC bulletins, for example, specifically recommend against reliance on penicillin in cases of systemic anthrax toxemia.

The Miss Marple of SUNY/Purchase does no better when it comes to divining an overarching motive for last fall's bacteriological assaults. The deed was done by a Pentagon budget hawk who "must have realized in advance that the anthrax attack would result in the strengthening of U.S. defense and response capabilities," Rosenberg conjectures. "This is not likely to have been a goal of anti-American terrorists." And the anti-American terrorists who flew two Boeing 757s into the side of the World Trade Center, one week before the first New Jersey-postmarked anthrax letters were mailed -- those people did not suppose their actions would provoke a massive American military response? Perhaps Mohamed Atta, too, was a rogue, right-wing subcontractor for the CIA? Rosenberg's logic is elusive.

Federal investigators, for their part, arrive at much the same conclusion, though by reverse direction. The anthrax mailings were insufficiently provocative, a "senior administration official" has told the Wall Street Journal, explaining his colleagues' basic assumption: "Al Qaeda is into mass casualties, not this junior-varsity, onesy-twosey terrorism." This would make the suspect's identity contingent on the body count he achieved, something he could not possibly have predicted; the logic here seems nonexistent. What if the anthrax mailer had managed, as intended, to assassinate the majority leader of the United States Senate? Would that have been senior varsity enough for the FBI?

10) So who did send the anthrax? What are you saying?

Simply this: Based on the publicly available evidence, there appears to be no convincing rationale for the FBI's nearly exclusive concentration on American suspects. And the possibility is far from foreclosed that the anthrax bioterrorist was just who he said he was: a Muslim, impliedly from overseas, who thought the events of "09-11-01" were something to be celebrated -- and who would have been doubly pleased to see "you die now."

David Tell is opinion editor of The Weekly Standard.