Click for graph of anthrax cases in the United States from 1952 through 2002.

Epidemiologists are often called "disease detectives," using many of the same methods as regular detectives to determine the cause of disease outbreaks, epidemics (i.e., larger excess in disease cases), or even pandemics (i.e., worldwide excess in disease cases).  The anthrax outbreak in the United States which occurred during the latter part of 2001 has many of the same characteristics as a typical outbreak.  What is different, however, is that there was no transmission from infected to susceptible persons that linked one case with another.  Instead, all of the cases were generated by a terrorist or group of terrorists who sent letters containing anthrax spores through the postal system.  These spores -- very small in size -- typically entered the skin or lungs or victim when the envelop was handled or opened, when coming in contact with an environment where envelopes had previously been handled or opened, or when passing through small holes in unopened envelops. 

Intentionally infecting others with a deadly disease is a criminal matter, typically addressed by the police.  Because the cases occurred in more than one state and involved the United States Postal System, the Federal Bureau of Investigation (FBI) was assigned as police detectives.  Yet harm to the victims (namely, sickness and death) was caused by Bacillus anthracis, requiring knowledgeable disease rather than police detectives.  This role was filled by epidemiologists from the United States Centers for Disease Control (CDC). 

While police detectives and disease detectives employ similar methods of investigation, the use of their findings is far different.  Police detectives typically keep information secret or under wraps, allowing them to build a legal case against the alleged criminal.  Eventually the information becomes public, but only when presented in a court of law.  Their intent in the American legal system is to convict and then punish the criminal, with hope that such actions will prevent future crimes. 

Disease detectives typically have a different goal, although related.  They usually try to figure out what went wrong in a social or physical environment, identifying factors that allow a disease agent to generating an outbreak or epidemic. The goal of the disease detective is first to contain the outbreak and then to educate people on how to prevent similar outbreaks in the future.  By necessity, these containment and education efforts  involve the general public.  Thus disease detectives work closely with the news media who as effective speakers and writers are best able to transmit educational messages.  Thus disease detectives tend to be more open and collaborative then police detectives.   When faced with a bioterrorist, however, police detectives and disease detectives share a goal, namely to find and stop the responsible terrorist or group of terrorists. The nature and occasional difficulties of such collaboration are described in the Anthrax media section of the UCLA Bioterrorism website. 

CDC informed the public in many ways, occasionally via interviews with reporters, other times in talks or professional presentations, but most often with updates in the Morbidity and Mortality Weekly Report (MMWR). 

  • The first such report was issued on October 12, 2001 following the finding on October 4 of a case of anthrax in Florida.

  • A second update was published on October 19, 2001, stressing that the early cases were due to the intentional release of B. anthracis, different from a conventional outbreak. 

  • CDC's third update came on October 26, 2001 with both case data and educational information on the management of anthrax exposure.

  • A fourth update arrived on November 2, 2001.  It included a graph of likely onset times for the 21 cases (16 confirmed and 5 suspect) that were identified at that time, linking most of them to three anthrax-laden letters sent earlier.

  • A week later on November 9, 2001 a fifth update was published, with information about 22 cases (the size of the outbreak at that time) and on adverse events that occur following mass treatment to prevent symptoms of anthrax. 

  • A sixth update appeared on November 16, 2001 with guidance on who should receive preventive treatment for anthrax. The November 16 report also cited efforts that were being made by CDC to assist foreign countries concerned with anthrax and terrorist activities. 

  • A seventh update was issued on November 30, 2001 on the 23rd anthrax case, arising under mysterious circumstances in Connecticut. 

  • An eighth update also appeared on November 30, 2001, but focused on adverse events that followed mass treatment of postal workers who were potentially exposed to anthrax. 

  • A previously suspected case was removed by CDC in a ninth update of December 7, 2001, reducing the outbreak to 22 probable cases.

  • Test results for anthrax contamination of the Brentwood Mail Processing and Distribution Center in the District of Columbia was presented by CDC in a tenth update of December 21, 2001.  These findings helped explain why four local postal workers developed inhalation anthrax.

  • An eleventh update also appeared on December 21, 2001, providing additional information on therapy and vaccination for persons exposed to anthrax spores. 

  • Many months later a twelfth update on April 5, 2002 described a laboratory worker in Texas who developed cutaneous anthrax when handling a vial with spores from the Anthrax outbreak.   

  • On June 7, 2002, a thirteenth update presented the follow-up examination of the Texas laboratory worker, who officially was designated by CDC as a confirmed case of cutaneous anthrax.

  • To provide medical protection for workers responsible for making B. anthracis-contaminated buildings safe for others to enter and occupy, CDC published a fourteenth update on September 6, 2002.

  • Following up on US Postal Workers in the District of Colombia who were exposed to Anthrax, CDC published an update on October 3, 2003.

During the months that followed the outbreak, CDC continued its investigation, using new techniques for handling and measuring the anthrax agent.  The October, 2002 issue of Emerging Infectious Diseases (Vol. 8, No. 10) was devoted to bioterrorism-related anthrax and summarized the work of CDC during the past year. 

The Disease Detective site presents clinical, epidemiologic, and media information on the 23 cases (19 confirmed, 4 suspect), including the one accidental laboratory case, which comprised the American anthrax outbreak of 2001. Included are graphs that disease detectives create to focus attention on the likely web of disease causation.  While sources are usually cited, responsibility for content and presentation lies with Professor R.R. Frerichs.  

Web detectives

Click green box for anthrax analysis of Ed Lake

Click green box for anthrax analysis of Richard M. Smith

Click for news account of the outbreak investigation (12/26/01)

Click for news account of temporal order that cases unfolded (12/26/01)