First case of bioterrorism-related inhalational anthrax in the United States, Palm Beach County, Florida, 2001 - Bioterrorism-Related Anthrax

Emerging Infectious Diseases, Oct, 2002 by Marc S. Traeger, Steven T. Wiersma, Nancy E. Rosenstein, Jean M. Malecki, Colin W. Shepard, Pratima L. Raghunathan, Segaran P. Pillai, Tanja Popovic, Conrad P. Quinn, Richard F. Meyer, Sharif R. Zaki, Savita Kumar, Sherrie M. Bruce, James J. Sejvar, Peter M. Dull, Bruce C. Tierney, Joshua D. Jones, Bradley A. Perkins

On October 4, 2001, we confirmed the first bioterrorism-related anthrax case identified in the United States in a resident of Palm Beach County, Florida. Epidemiologic investigation indicated that exposure occurred at the workplace through intentionally contaminated mail. One additional case of inhalational anthrax was identified from the index patient's workplace. Among 1,076 nasal cultures performed to assess exposure, Bacillus anthracis was isolated from a co-worker later confirmed as being infected, as well as from an asymptomatic mail-handler in the same workplace. Environmental cultures for B. anthracis showed contamination at the workplace and six county postal facilities. Environmental and nasal swab cultures were useful epidemiologic tools that helped direct the investigation towards the infection source and transmission vehicle. We identified 1,114 persons at risk and offered antimicrobial prophylaxis.

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In Florida, human anthrax has been rare; among eight human cases reported in Florida in the 20th century, the most recent was a cutaneous case in 1974 (1). On October 2, 2001, a 63-year-old Florida man was hospitalized for a non-localizing severe illness that began 2 days earlier, characterized by fever, chills, sweats, fatigue, and malaise, which progressed to vomiting, confusion, and incoherent speech. No history of cough, dyspnea, abdominal pain, diarrhea, or skin lesions was reported. On October 4, the Florida Department of Health (FDOH) Bureau of Laboratories confirmed B. anthracis from a culture of cerebrospinal fluid. The patient's condition deteriorated, and he died 3 days after admission (2).

After anthrax was confirmed and in consideration of possible bioterrorism, we initiated an investigation to determine the extent and source of the event, develop control strategies, and protect potentially exposed persons. This report summarizes the findings of our epidemiologic investigation.

Methods

Case Investigation

We performed a detailed investigation of the index patient's exposures during the 60 days before his illness. We visually inspected and obtained culture specimens for Bacillus anthracis at locations he visited during the 60-day period, including his home, recreational destinations, retail outlets patronized, and workplace. Initial samples from the workplace were from the patient's work area and the company mailroom and photo library, as well as air ventilation filters.

Case-Finding and Surveillance

A confirmed case of anthrax was defined as a clinically compatible cutaneous, inhalational, or gastrointestinal illness confirmed as anthrax by laboratory tests, including 1) isolation of B. anthracis from an affected tissue or site or 2) other laboratory evidence of B. anthracis infection based on at least two supportive laboratory tests (3). Supportive laboratory tests included polymerase chain reaction (PCR) (4) of DNA from patient fluid from a normally sterile site, immunohistochemical staining of patient tissue samples, and enzyme-linked immunosorbent assay serologic tests to detect immunoglobulin G (IgG) response to B. anthracis protective antigen (PA) (5).

We implemented case-finding through daily chart review in Palm Beach County intensive-care units (ICUs) and regionally in ICUs in North Carolina, where the index patient had traveled during the potential exposure period. ICU patients who had blood or cerebrospinal fluid cultures performed within 24 hours of hospital admission had more detailed chart reviews and interviews. If anthrax was not ruled out, further interviews were done with patients, family members, and medical providers. Laboratory testing for B. anthracis and other potentially causative pathogens was offered if indicated. Nearby counties implemented similar case-finding efforts in ICUs and emergency departments.

We initiated enhanced surveillance locally through alerts to medical examiners and statewide through requests to laboratory directors to forward to the FDOH laboratories any cultures suspicious for Bacillus species isolated from sterile sites. A statewide veterinary alert was issued for cases of anthrax in animals. All case-finding surveillance was retrospective to September 11, 2001, and prospective beginning October 5.

Surveillance in Potentially Exposed Groups

Workplace-exposed persons were defined as those who, within 60 days of onset of illness in the index patient, spent >1 h in the building where he worked. On October 3 through the employer, on October 8 through press releases and media briefings, and on October 8-10, 13, 17, and 19 through information bulletins, we asked workplace-exposed persons and medical personnel caring for them to report influenzalike illness or skin lesions to the FDOH. Beginning October 8, hospitals were notified through infection-control professionals and public health alerts.

We obtained nasal swabs from workplace-exposed persons while dispensing prophylactic antibiotics on October 8-10 and from workers who handled trash at the workplace on October 13. Immediately after specimens were obtained, nasal swabs were applied to sheep-blood agar culture medium plates and transported to the Florida Public Health Laboratory. B. anthracis was confirmed in nonmotile, nonhemolytic isolates by gamma-phage lysis and PCR and later by detection of B. anthracis capsule and cell-wall antigens with direct fluorescent antibody tests. Testing for serum IgG antibody response to the PA component of the anthrax toxins was offered on October 10, 13, 17, and 19 to workplace-exposed persons.