about Epidemiology & the department

Epidemiology academic information

Epidemiology faculty

Epidemilogy resources

sites of interest to Epidemiology professionals

Last Updated

04 Nov 2002

Source: Federation of American Scientists, December 10, 2001.

A Compilation of Evidence and Comments on the Source of the Mailed Anthrax

Barbara Hatch Rosenberg, Federation of American Scientists (revised December 10, 2001)

All the available evidence indicates that the source of the mailed anthrax, or the information and materials to make it, is a US government program.


  • All letter samples contain the same strain of anthrax, corresponding to the AMES strain in the N. Arizona State University database (which has been used for identification). The Ames substrain possessed by N. Arizona State is referred to herein as the "reference strain." That strain was obtained from Porton Down (UK) in the mid-90's (the sample was marked "October 1932"); Porton had gotten it from Fort Detrick.

  • A 2000 paper by M. Hugh-Jones, PJ Jackson, P. Keim et al says that the Ames strain played a central role in the US BW program [i.e., before 1969]. Hugh-Jones says he learned that from David Huxsoll, Former Commander, USAMRIID. However, he says Vollum 1B was the strain stockpiled (at least in the early days of the US biological weapons program). The search for better strains undoubtedly continued, leading the US program to prefer the Ames strain because of its high virulence.

  • The Ames strain is used now in the US biodefense program for testing vaccines etc.

  • The Ames reference strain in the N. Arizona collection is probably the earliest Ames substrain (isolated in 1925 and sealed in 1928, perhaps subcultured in 1932).

  • There are at least four Ames substrains, all under the control of Fort Detrick. They were isolated by laboratories in Ames, Iowa but were not subsequently studied or distributed by them.

  • Undoubtedly the confusion about Ames substrains could be cleared up by USAMRIID, but they have been evasive.


  • "Weaponization" is used here to mean preparation of the form of anthrax found in the Daschle letter: fine particles, very narrow size range, treated to eliminate static charge so it won't clump and will float in the air. The weaponization process used was extraordinarily effective. The particles have a narrow size range (1.5-3 microns diameter), typical of the US process.

  • The extraordinary concentration (one trillion spores per gram) and purity of the letter anthrax is believed to be characteristic of material made by the US process.

  • A reporter who writes on anthrax vaccine has privately stated that four labs have told him that under the electron microscope the appearance of the sample is like that of unmilled anthrax spores. Milled samples are identifiable because they contain debris. The optimal US process did not use milling.

  • The US weaponization process is secret-Bill Patrick, its inventor, says it involves a COMBINATION of chemicals.

  • The Armed Forces Institute of Pathology (Washington DC) is studying the anthrax using an energy dispersive X-ray spectroscope, which can detect the presence of extremely tiny quantities of chemicals; traces of several chemicals have been found.

  • The Senate sample contains a special form of silica used in the US process. It does not contain bentonite (used by the Iraqis).

  • All the letters probably contained the same material. The clumping of the anthrax in the two letters mailed on Sept 18 (to NBC and the NY Post) probably resulted from the letters getting wet in the course of mail processing or delivery, according to Army scientists. This conclusion is strengthened by the similarity of the Florida anthrax (the first to be observed, probably also mailed on Sept 18) to that in the Daschle letter, mailed Oct 9.


  • A study of genetic drift at certain locations in anthrax is underway at Northern Arizona State University. The results are expected to give an idea of how many times the letter anthrax had replicated, in comparison to the reference strain-ie, whether it was grown on a very large scale (as in a State program) or on a very small scale, as would be likely if recently made by a terrorist.

  • Analysis of trace contaminants could also indicate the scale/method of production (ie, liquid medium, in a fermenter, or solid medium, on petri dishes, a likely method for small-scale preparation).


  • It has just been reported that the complete sequence has been determined for the genomes of both the anthrax used in the Florida attack and the Ames reference strain to which it corresponds. This work was done under government contract by the Institute for Genomic Research, a private non-profit organization. The results have not been made public but they are in government hands and there has been no retraction of the oft-repeated official statement that the letter anthrax matches the Ames reference strain.

  • In addition, sequence data will reveal whether the Ames reference strain is a mixture of types, as sequencing has revealed to be the case for another anthrax strain. If so, the proportions of the mixture may differ from lab to lab and could be used to identify the source.

  • Senator Bob Graham, Chairman of the Senate Intelligence Committee, said in late October that investigators can identify with great certainty which lab produced the anthrax, but it will be a laborious, time-consuming process. (Chicago Tribune, 27 Oct 01).


  • Contrary to early speculation, there are no more than about 20 laboratories known to have obtained the Ames strain from Fort Detrick. The names of 15 of these laboratories have been found in the open literature (see Appendix). Of these, probably only about four in the US might possibly have the capability for weaponizing anthrax. These include both US military laboratories and government contractors.


  • Analysts believe the letters were not written by a Middle-Easterner. The FBI publicly conjectures that the perpetrator was a lone, male domestic terrorist, obviously one with a scientific background and lab experience who could handle hazardous materials.

  • The perpetrator must have received anthrax vaccine recently (it requires a yearly booster shot), whether or not he made the material himself, because filling the letters was a dangerous operation. The vaccine is in short supply and is not generally accessible. Vaccination records must be available.

  • The perpetrator appears to be a forensic expert. In preparing and mailing the letters he successfully covered every personal trace.


  • There was only one week between Sept 11 and Sept 18, when the first two letters (and probably another letter, never found, to AMI) were postmarked. This suggests that the anthrax was already in hand before Sept 11.

  • Did the perpetrator have advance knowledge of the Sept 11 attacks? Secretary of Defense Rumsfeld has said that he does not believe al Qaeda was responsible for the anthrax attack, and other public officials have increasingly indicated that the perpetrator was probably domestic.


  • At first, US officials provided miscellaneous bits of information, some conflicting; then denied some of the earlier information, then clammed up. They now have a great deal of information that has not been made public. Under pressure from leaks, they have started a gradual release of information again.

  • The US rejected a UN resolution offered by France to condemn the anthrax attack, on the grounds that it could have been domestic terrorism.

  • The Secretary of Health and Human Services said in October that some of the relevant information is classified, and some is restricted by the FBI.

  • John Bolton, Under Secretary of State for Arms Control and International Security, spoke on Nov. 19 at the opening of the five-yearly Review Conference of the Biological Weapons Convention in Geneva. At a press conference following his talk, he said "We don't know, as I say in the statement, at the moment, in a way that we could make public, where the anthrax attacks came from." This statement, as well as other information, indicates that US officials DO know where the anthrax came from.

  • The FBI says it is now investigating government and contractor laboratories possessing the Ames strain, and individuals who had access to them. Col. Arthur Friedlander, Sr. Research Scientist at USAMRIID, said no one there knows how to make dry weaponsized anthrax.

  • According to the New York Times (2 Dec 01), a law enforcement official close to the federal investigation called the concept of a government insider, or someone in contact with an insider, "the most likely hypothesis…it's definitely reasonable." An American official sympathetic to this thesis was quoted in the same article saying that, in addition to military laboratories, "there are other government and contractor facilities that do classified work with access to dangerous strains, but it's highly likely that the material in the anthrax letters came from a person or persons who really had great expertise. We haven't seen any other artifacts that point us elsewhere."

  • Senate Majority Leader Thomas Daschle, recipient of one of the anthrax letters, has been in frequent contact with investigators. He said on Dec 8 that the perpetrator was probably someone with a military background.


  • The perpetrator is probably an American microbiologist who has access to weaponized anthrax or to the expertise and materials for making it, in a US government or contractor lab. He does not live in or near Trenton, but more probably in the Washington, DC area. Trenton is probably accessible to him (it is a stop on the Amtrak line that runs along the East coast), but if he is smart enough to handle anthrax he is smart enough not to mail it from his home town.

  • The anthrax in the letters was probably made and weaponized in a US government or contractor lab. It might have been made recently by the perpetrator on his own, or made as part of the US biodefense program; or it may be a remnant of the US biological weapons program before Nixon terminated the program in 1969.

    • Weaponization of dry anthrax after 1972, when the Biological Weapons Convention was signed, could be construed as a violation of the Convention.

  • The motive of the perpetrator was not necessarily to kill but to create public fear, thereby raising the profile of BW. He simply took advantage of Sept 11 to throw suspicion elsewhere. The letters warned of anthrax or the need to take antibiotics, making it possible for those who handled the letters to protect themselves; and it seems unlikely that the perpetrator would have anticipated that the rough treatment of mail in letter sorters etc, would force anthrax spores through the pores of the envelopes (which were taped to keep the anthrax inside) and infect postal workers and others.

    • The choice of media as targets seems to have been cleverly designed to ensure publicity about the threat of biological weapons. One can only speculate that the perpetrator may have wished to push the US government toward retaliatory action against some enemy, or to attract funding or recognition to some program with which he is associated.

    • The choice of Senators Daschle and Leahy as targets may be a clue that has yet to be deciphered.

  • The US government has undoubtedly known for some time that the anthrax terrorism was an inside job. They may be reluctant to admit this. They also may not yet have adequate hard evidence to convict the perpetrator.

    • In opposition to most of the countries of the world, the Bush administration turned down a Protocol to monitor compliance with the ban on biological weapons last July. In so doing it reversed the policy of the previous three administrations aimed at strengthening the Biological Weapons Convention, which lacks verification measures. The action put the US at odds with most of its allies and fueled accusations of US unilateralism, according to the Washington Times (Dec 5).

    • The anthrax attacks have had no effect on administration policy. At the start of a five-yearly Biological Weapons Convention Review Conference last month, Under-Secretary Bolton caused dissention by accusing several parties to the Convention of violating it. On Dec 7, the last day of the conference, the US doublecrossed its European allies by reversing a compromise agreement of the previous day, thereby causing an uproar and derailing the Conference. According to European diplomats, failure of the conference sends the message that the international community is not willing to enforce the ban on biological weapons.

  • Conclusions: A recent report by the Congressional GAO, as well as many recent statements by military and non-governmental experts in the BW field, holds that terrorists are unlikely to be able to mount a major biological attack without substantial assistance from a government sponsor. The recent anthrax attack was a minor one but nonetheless we now see that it was perpetrated with the unwitting assistance of a sophisticated government program. It is reassuring to know that it was not perpetrated by a lone terrorist without state support.

    • It is not reassuring, however, to discover that a secret US program may have been the source of that support, and that security is so dangerously lax in military or defense contractor laboratories. US government insistence on pursuing and maintaining the secrecy of elaborate biological threat assessment activities is undermining the prohibitions of the Biological Weapons Convention and encouraging biological weapons proliferation in other countries, which in turn may support bioterrorist attacks on the American public.


(Information obtained from open sources)

  1. USArmy Medical Research Institute for Infectious Diseases (Ft. Detrick, MD)#,*

  2. Dugway Proving Ground (Utah)#,*

  3. Naval Research Medical Center and associated military labs (MD)#

  4. Battelle Memorial Institute (Ohio; plus laboratories in many other locations)#,*

  5. Duke University Medical School, Clinical Microbiology Lab. (NC)

  6. VA Medical Center, Durham (NC)

  7. USDA laboratory and Iowa State College of Veterinary Medicine, Ames (Iowa)

  8. LSU College of Veterinary Medicine*

  9. Northern Arizona State University (Arizona)*

  10. Illinois Institute of Technology Research Institute (IL)

  11. University of New Mexico Health Sciences Center, Albuquerque (NM)*

  12. Institute for Genomic Research (MD)

  13. Chemical and Biological Defense Establishment, Porton Down (UK)*

  14. Center for Applied Microbiology and Research, Porton (UK)*

  15. Defense Research Establishment, Suffield (CA)*

In addition, CDC, NIH, and Los Alamos and a few others may have the Ames strain.

* Obtained through a FOIA request by the Washington Post (article Nov 30, 01)

# indicates laboratories in the US that are probably more likely than the others to have weaponization capabilities.