Epidemiologic investigations of bioterrorism-related anthrax, New Jersey, 2001 - Bioterrorism-Related Anthrax

Emerging Infectious Diseases, Oct, 2002 by Carolyn M. Greene, Jennita Reefhuis, Christina Tan, Anthony E. Fiore, Susan Goldstein, Michael J. Beach, Stephen C. Redd, David Valiante, Gregory Burr, James Buehler, Robert W. Pinner, Eddy Bresnitz, Beth P. bell

At least four Bacillus anthracis-containing envelopes destined for New York City and Washington, D.C. were processed at the Trenton Processing and Distribution Center (PDC) on September 18 and October 9, 2001. When cutaneous anthrax was confirmed in a Trenton postal worker, the PDC was closed. Four cutaneous and two inhalational anthrax cases were identified. Five patients were hospitalized; none died. Four were PDC employees; the others handled or received mail processed them. Onset dates occurred in two clusters following envelope processing at the PDC. The attack rate among the 170 employees present when the B. anthracis-containing letters were sorted on October 9 was 1.2%. Of 137 PDC environmental samples, 57 (42%) were positive. Five (10%) of 50 local post offices each yielded one positive sample. Cutaneous or inhalational anthrax developed in four postal employees at a facility where B. anthracis-containing letters were processed. Cross-contaminated mail or equipment was the likely source of infection in two other case-patients with cutaneous anthrax.

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On October 4, 2001, inhalational anthrax was diagnosed in a Florida man who had no known exposure risk factors (1). The following week, cases of cutaneous anthrax in persons exposed to letters containing a suspicious powder were reported in New York City. The initial investigation showed that four envelopes containing Bacillus anthracis spores were mailed through the U. S. Postal Service (USPS) to media outlets in New York City and senate offices in Washington, D.C., in September and October 2001. These four recovered envelopes were postmarked at the USPS Trenton Processing and Distribution Center (Trenton PDC) in New Jersey.

On October 18, cutaneous anthrax was confirmed in a New Jersey postal worker. This prompted the closure of the Trenton PDC and initiation of an investigation in New Jersey. The objectives of the investigation were to determine the extent of the anthrax outbreak in New Jersey, assess potential sources of B. anthracis exposure, and prevent additional cases by developing and implementing control measures.

Methods

Case Definitions

In this multistate outbreak, all sites adopted the Centers for Disease Control and Prevention (CDC) case definitions for anthrax (2). A confirmed case was defined as a clinically compatible illness that was laboratory confirmed either by isolation of B. anthracis from an affected tissue or site, or by two supportive laboratory tests. A suspected case was defined as a clinically compatible illness with no isolation of B. anthracis and no alternative diagnosis, but with one positive supportive laboratory test or a clinically compatible illness epidemiologically linked to a confirmed environmental exposure to B. anthracis.

Supportive laboratory tests included demonstration of B. anthracis in a clinical specimen by immunohistochemical staining; detection of B. anthracis DNA by polymerase chain reaction from specimens collected from an affected tissue or site; or the presence of anti-protective antigen immunoglobulin G (anti-PA IgG) by enzyme-linked immunoadsorbent assay (3).

Case Investigations

Suspected and confirmed case-patients were interviewed about symptoms, employment, and other possible exposures, and their medical records were reviewed. Coworkers and supervisors were also interviewed. For case-patients who were USPS employees, job assignments and time sheets were reviewed, with special attention to dates when letters containing anthrax spores were postmarked. Blood, tissue, and microbiologic samples were obtained and sent for testing. When possible, the incubation period was defined as the time between the date of likely exposure to spore-containing envelopes and the onset of symptoms.

Surveillance

Initial case finding involved investigation of potential cases reported by health-care providers, hospitals, and the public directly to the health department. Subsequently, we initiated stimulated passive hospital-based surveillance to identify additional inhalational anthrax cases (4). Infection control professionals from 61 hospitals in 15 counties in New Jersey, Pennsylvania, and Delaware, serving an area of 6.7 million residents, provided daily totals of emergency department and intensive-care unit admissions and reported all patients meeting broad clinical criteria (such as respiratory failure or febrile illness without a confirmed alternative diagnosis) for possible inhalational anthrax. Passive surveillance for both inhalational and cutaneous anthrax cases was conducted statewide in New Jersey and in parts of Pennsylvania and Delaware that are contiguous to New Jersey. Surveillance was enhanced through electronic communication with local health departments, press releases, and postings on websites of the New Jersey Department of Health and Senior Services (NJDHSS) and two New Jersey medical associations. All persons with possible anthrax identified through surveillance were followed up through telephone calls to the patients, the physicians and nurses treating them, and requests for laboratory specimens.