Opinion: I worked on the CDC investigation of the anthrax letters. 25 years later, are we ready for the next biothreat?

Twenty-five years ago, as the country still reeled from Sept. 11, the first of two batches of anthrax-laden envelopes was mailed from New Jersey to news media and congressional offices. All told, the letters caused 22 cases of anthrax disease and five deaths, prompted considerable fear in the U.S., and cost billions of dollars in response and recovery. Remembering how public health responded to the anthrax letters can help inform how we might meet the challenge of something similar today, whether intentional or inadvertent, and whether human or artificially generated.

The 2001 anthrax attacks showed how a handful of letters could produce an enormous impact. Everyone gets mail, and the marvel of the postal system's reach and distribution was intentionally used as an anthrax dissemination machine. One powder-containing envelope was delivered to American Media Incorporated in Florida, where a photo editor for The Sun tabloid became severely ill, leading an astute clinician to suspect anthrax based on what he saw in a spinal tap specimen. When the CDC was alerted the next day through its newly established Laboratory Response Network, the author and colleagues began their work. Initially, the investigation focused on possible natural exposures as the source. However, when a second AMI employee was confirmed with anthrax, only weeks following the Sept. 11 attacks, bioterrorism became front and center, leaving the team a little stunned and wondering how large and coordinated the attack might be. The CDC then stood up an Emergency Operations Center in one of its auditoriums, sent multiple teams to the field, and the author began serving as lead of the Epidemiology and Surveillance Team at the EOC.

After the investigation, the author and colleagues published a paper describing the anthrax cases from contaminated mail. The clinical picture was unusual: half of the cases were limited skin infection, while the rest were highly fatal inhalational disease. Molecular testing, something relatively novel at the time, was used to show that isolates recovered from patients, from four powder-containing envelopes, and from environmental samples were indistinguishable, indicating a common source. The investigation also identified important differences between the two major mailings: illnesses associated with the Sept. 18 mailing were more often cutaneous and associated with media workplaces—what they informally called 'crunchy' anthrax since it was clumped—while the Oct. 9 mailing was associated with more inhalational disease and illness among postal workers along the mail-processing pathway—what they called 'fine powder' anthrax, which was more easily aerosolized.

The findings showed that the consequences of an intentional biological release went far beyond the intended targets and that the characteristics of the agent, its formulation, the route of dissemination, and the population exposed likely had an important impact on the clinical and epidemiologic picture.