Last Updated

29 Nov 2002

    Source: Suspected Cutaneous Anthrax in a Laboratory Worker -- Texas, 2002, MMWR 51(13);279-281,  April 5, 2002

The likely cutaneous anthrax case occurred in a laboratory worker in Texas. On March 6, 2002, the National Institute for Occupational Safety and Health (NIOSH) of CDC received a request from the director of the Texas laboratory to assist in the evaluation of a worker who had been diagnosed with cutaneous anthrax. The laboratory had been provisionally approved to process environmental samples for Bacillus anthracis in support of CDC investigations of the bioterrorist attacks in the United States during fall 2001. Since March 7, CDC has interviewed the ill laboratory worker and other workers at the laboratory and conducted environmental assessments of the workplace. This report summarizes the epidemiologic and environmental investigation of this case. 

The laboratory worker was one of three employees of the laboratory who had primary responsibility for processing environmental B. anthracis specimens. Neither this worker nor any of the other approximately 40 employees of the laboratory had received anthrax vaccine. The laboratory worker did not handle B. anthracis-containing samples or cultures during February 19--28. On February 28, he cut a small bump on his right jaw while shaving, which bled briefly and then became itchy and irritated. On March 1, he assisted a co-worker moving vials containing aliquots of confirmed B. anthracis isolates from the biological safety cabinet (BSC) in the main laboratory to the freezer in an adjacent room. The co-worker had transferred the isolates from blood agar plates to the vials by collecting the growth with a swab. The co-worker removed the vials from the BSC and handed them to the patient. Without gloves, the patient took the vials from the co-worker, placed the vials in the freezer, and then washed his hands with soap and water. During the next 2--3 days, the worker's facial wound increased in size and developed a scab. He also reported right cervical adenopathy, a low-grade fever, and swelling and erythema on his right cheek and neck. The patient's health-care provider obtained a swab of the area underneath the scab and of the area under a vesicle, without cleansing the skin first. The health-care provider made a presumptive diagnosis of cutaneous anthrax and the patient was administered a 2-week course of ciprofloxacin.

The culture of this specimen was positive for B. anthracis on testing at Laboratory A and CDC. Because of culture results, the patient was admitted to the hospital on March 5 and treated with intravenous ciprofloxacin and doxycycline pending antimicrobial susceptibility testing. The lesion developed the characteristic eschar of cutaneous anthrax (see figure at left). A chest radiograph performed on admission demonstrated possible fullness of the mediastinum, but computed tomography of the chest was normal. The isolate was susceptible to ciprofloxacin and doxycycline, and the patient continued receiving ciprofloxacin. The patient's symptoms improved during hospitalization, and he was discharged on March 9. Serologic studies for antibodies to B. anthracis are planned.

On March 5, the laboratory's certified industrial hygienist (CIH) performed environmental sampling of both the laboratory and the patient's residence. Seven wipe samples were taken at the laboratory (i.e., the top of the vials the patient had handled, the key to the freezer where the vials were placed, the doorknob of the freezer room, the centrifuge where specimens are prepared, the two BSCs where specimens are handled, and surfaces in the patient's office in the laboratory). Seven additional samples were taken at the patient's residence. The CIH then cleaned surfaces and equipment throughout the laboratory and the patient's residence by using a disinfectant containing a phenolic and a quaternary ammonium compound, which are not sporicidal. The environmental samples were analyzed in the laboratory. All samples were negative except the wipe sample collected from tops of the vials that the patient had handled, which was positive for B. anthracis. Confirmation of the vial top specimen at CDC is planned.

Workers at the laboratory reported that specimen processing of environmental samples suspected of containing B. anthracis is done under Biosafety Level 3 (BSL-3) conditions. These samples, including swab, wipe, dust (collected onto filter media by a vacuum), and air samples, are opened in a Class II, Type A BSC in a room designated for acid-fast bacillus specimens (AFB room). Personal protective equipment for procedures performed in this room includes disposable, fluid-resistant laboratory coats, gloves, and either a NIOSH-certified N95 or P100 disposable, filtering-facepiece respirator, which are disposed of into a biohazard container before exiting the room. Work with purified B. anthracis cultures is performed in a separate BSC located in the main laboratory room. Personal protective equipment at this workstation consists of gloves and a laboratory coat. Aliquots of confirmed isolates of B. anthracis are placed in vials and stored in a locked freezer in a room located off the main laboratory. A 10% bleach solution is routinely used to decontaminate surfaces after processing specimens potentially containing B. anthracis. However, because bleach caused labels to become dislodged, storage vials had been sprayed with 70% isopropyl alcohol instead of being wiped with bleach. By the time of the CDC site visit, the laboratory personnel had obtained labels for storage vials that would not dislodge with bleach.

On March 7 and 8, CDC interviewed the laboratory workers; none reported illness among other employees or their family members. CDC also conducted environmental sampling at the laboratory on March 7, consisting of 40 surface wipe and 36 air samples. Wipe samples obtained with sterile polyester/rayon pads, moistened with sterile water, were collected from various surfaces in the laboratory and in the adjacent office area, including desks, flooring, door knobs, BSCs, heating, ventilation, air-conditioning return air grills, and laboratory equipment (including the centrifuge and shaker used for processing environmental samples). Air samples were collected in three locations in the laboratory: the AFB room, the area adjacent to the BSC used for anthrax work, and the general microbiology area; two locations in the adjacent office area; and outdoors. All environmental samples were negative for B. anthracis at CDC.

On March 8, CDC performed a building assessment, including a ventilation survey, airflow distribution mapping, and BSC characterization. The AFB room was not under negative pressure in relation to adjacent areas of the main laboratory; however, the laboratory was under negative pressure relative to the outside and to the adjacent office areas. The BSCs were functioning adequately.

In summary,  the likely source of exposure was the surface of vials containing B. anthracis isolates that the worker placed in a freezer on March 1.

Return to Case Addenda