CDC update on potential anthrax exposures

The Centers for Disease Control and Prevention (CDC) has completed additional work to further define the risk of anthrax for employees potentially exposed because best safety practices were not followed in one of its laboratories in early June.   Based on the results of some of this follow-up work, most of the impacted employees have been determined to have no increased risk of exposure as a result of this incident, and therefore are being advised that they no longer need to take antibiotics and vaccine to prevent inhalation anthrax.

Some Atlanta-based staff were being monitored and provided or prescribed antibiotics because they may have been unintentionally exposed to live anthrax bacteria after established safety practices were not followed during a laboratory procedure (CDC Anthrax Release ) This broad action was taken out of an abundance of caution, and the agency began immediate work to better determine employees’ potential risk by administering a detailed epidemiologic questionnaire to those believed to be affected to learn more about their whereabouts and their specific work during the time of potential exposure – June 6 to June 13.

In addition to the epidemiologic survey, CDC conducted environmental sampling of surfaces in the affected areas and also performed additional studies to learn if the bacterial samples might have been inactivated when they were taken out of the BSL 3 laboratory.   All of this work is being used to gain better information to advise employees about their need to take antibiotics to prevent anthrax.  None of the samples taken from laboratory surfaces in the potentially affected laboratories have been positive for anthrax.  Additional investigations on the procedure used to treat anthrax before it was transferred to lower-security laboratories have been reassuring, suggesting that while it is not impossible that viable anthrax was transferred out of the high-containment laboratory, it is extremely unlikely that this happened.

CDC officials have established two potential risk groups of individuals: staff who were potentially exposed to aerosols in affected laboratory space; and staff who were not potentially exposed to aerosols but were in or near affected laboratory space.  Employees in these groups are having one-on-one appointments with medical staff in CDC’s occupational health clinic who are reviewing all information with them and discussing the pros and cons of continuing post-exposure prophylaxis as part of shared decision making.  Other employees visited the CDC clinic and were determined not to be affected by the incident and therefore not included in one of the groups.  Twenty-nine individuals in group one are being advised to continue taking antibiotics out of an abundance of caution.  Thirty-three individuals taking antibiotics in group two are being advised that they can discontinue antibiotics.

CDC continues to respond to this incident.  The agency’s Associate Director for Science Dr. Harold Jaffe is leading an internal investigation into the circumstances surrounding this incident.  He will submit a report to CDC Director Dr. Tom Frieden in early July.  In addition, CDC has reported the incident to the Federal Select Agent Program and USDA’s Animal and Plant Health Inspection Service (APHIS), is conducting an independent investigation.  Based on these investigations, CDC will take appropriate action in the individual laboratory, as well as any actions indicated for all laboratories which work with dangerous microbes at CDC, and will consider broader implications for laboratory safety.

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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES