New review of anthrax case discussed by review committee vice chair, Stanford bioterrorism expert

In 2001, a mystery perpetrator mailed a series of anthrax-laced letters to several locations, killing five people. In 2008, shortly after emerging as the prime suspect in an exhaustive investigation by the FBI, an Army microbiologist, Bruce Ivins, PhD, committed suicide. This morning, a National Academy of Sciences committee, charged in September 2008 with reviewing the scientific approaches used by the FBI in that investigation, released its report. The report said that the scientific evidence, while consistent with the law-enforcement findings, did not provide definitive proof linking anthrax in Ivins’ lab to the letters. David Relman, MD, vice chair of the review committee, is a professor of microbiology and immunology and of infectious diseases at the Stanford University School of Medicine. He answered the questions below from Bruce Goldman, a science writer in the medical school’s communications office.

Q: Did your review uphold the FBI’s findings? Is this case still open?

Relman: The main conclusion by the FBI and Department of Justice of their scientific investigation was that the Bacillus anthracis in the letters was derived from a flask called RMR-1029, which was located in the laboratory of Dr. Bruce Ivins at the United States Army Medical Research Institute for Infectious Disease in Frederick, Md.

We found that the FBI did a lot of things well — they reached out to some of the best scientists in the world, they executed a variety of scientific procedures in a very capable fashion, they helped to promote the nascent field of microbial forensics and they dedicated considerable resources towards these goals.

However, we also found some problems and gaps in the scientific investigation. Although the scientific evidence was supportive of a link between the letters and that flask, it did not definitively demonstrate such a relationship, for a number of reasons. Our overarching finding was that it is not possible to reach a definitive conclusion about the origins of the B. anthracis in the mailings based on the available scientific evidence alone.

We were not asked, nor properly constituted as a committee, to judge the conduct of the law enforcement inquiry. In February 2010, the Justice Department closed its investigation of the anthrax mailings, concluding that Dr. Ivins had committed the attacks.

Q: Where did your own particular area of expertise get put into play in this review?

Relman: I have expertise in several relevant areas of science, including microbiology and microbial genomics, as well as in biological terrorism and the challenges of anticipating future biological threats.

Q: As I understand it, anthrax is a disease not uncommon among animals, such as cattle. Does the organism responsible for anthrax have to be substantially modified to become a bioterror weapon directed at humans?

Relman: Anthrax is generally a disease of herbivores (e.g., cattle, sheep, horses), which acquire the infection by grazing on contaminated soils. The disease is not contagious. Anthrax spores are highly resistant to environmental insults. These spores allow the bacterium to survive for long periods of time in soil. The course and outcome of human anthrax depend on dose and on whether the infection is acquired via the skin, gastrointestinal tract or inhalation. The most lethal manifestation of anthrax is due to inhalation of the spores, causing a highly fatal disease. When appropriately prepared, B. anthracis spores are attractive agents for biological warfare and bioterrorism because they can be produced in prodigious quantities in a form that is readily aerosolized and inhaled. Preparation and production of spores suitable for use as a weapon does not require unusual skills, equipment or reagents.

Q: What made this case, and the FBI’s investigation of it, so challenging?

Relman: After the tragic mailings of letters containing B. anthracis in 2001, the FBI began an extensive investigation involving many experts and tremendous resources and ultimately lasting more than eight years. Cases involving the use of a biological agent as a weapon are particularly challenging, given the complex biology of the weapon itself, the nascent state of microbial forensics and, in this case, the potential breadth and scope of the attack. The FBI expended over 600,000 investigator work hours, involving in excess of 10,000 witness interviews conducted on six continents, the execution of 80 searches and the recovery of over 6,000 items of potential evidence. The case involved the issuance of over 5,750 federal grand jury subpoenas and the collection of 5,730 environmental samples from 60 site locations. This investigation represented a shift in routine operations of the FBI as it reached out to the scientific community to assist.

In September of 2008, the FBI asked the National Academy of Sciences to convene a committee to conduct an independent review of the scientific approaches used during the Anthrax Letters investigation, and the conclusions drawn from them. We were not asked to assess the probative value of the scientific evidence, nor to offer any view on the guilt or innocence of any person(s) in connection with the case. Our committee was constituted with experts in the fields of microbiology, medicine, physical chemistry, statistics, biochemistry, public health, environmental studies, forensic science and jurisprudence. In July 2009, we met for what would prove to be the first of seven meetings. In the course of our 19-month study, the FBI provided us with approximately 9,600 pages of materials. With the release of our report today, all of these materials are now available to the public.

Q: Any thoughts on how a law-enforcement investigation of this nature should be conducted in the future?

Relman: While much of our effort was focused on a review of the science performed in support of the investigation of the 2001 B. anthracis mailings, an equally important goal has been to help ensure that future scientific investigations of biological attacks are conducted in the most relevant, rigorous and thoughtful manner possible.

Although the events of 2001 were tragic, they could have been much worse. In the future, among many other requirements, it will be important to ensure more timely results, more efficient environmental analysis, access to globally representative strain collections and a robust capability for characterizing less well-studied or less easily cultivated biological agents.

Officials may also need to manage expectations among the general public, policymakers and the scientific community about the conclusions that can realistically be expected from the use of microbial forensics.

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