CDC lab determines possible anthrax exposures; staff provided antibiotics/monitoring

The Centers for Disease Control and Prevention (CDC) announced yesterday that approximately 75 Atlanta-based staff are being monitored or provided antibiotics because they may have been unintentionally exposed to live Bacillus anthracis (anthrax) after established safety practices were not followed.

CDC is taking aggressive steps to protect the health of all involved, including providing protective courses of antibiotics for potentially exposed staff. Based on most of the potential exposure scenarios, the agency believes the risk of infection to be very low. Based on the review to date, CDC believes that other staff, family members, and the general public are not at risk of exposure and do not need to take any protective action.

Although the investigation continues, early reports show that one of CDC's Roybal campus biosafety level 3 (BSL3) labs was preparing B. anthracis samples for research in other CDC labs at lower biosafety levels to yield new means of detecting dangerous pathogens in environmental samples. However, the lab used a procedure that did not adequately inactivate the samples. The potentially infectious samples were moved and used for experimentation in three CDC Roybal campus laboratories not equipped to handle live B. anthracis. Workers, believing the samples were inactivated, were not wearing adequate personal protective equipment while handling the material.

Lab safety investigators also determined that, sometime between June 6 and June 13, procedures used in two of the three labs may have aerosolized the spores. Environmental sampling was done, lab and hallway areas were decontaminated, and laboratories will be re-opened when safe to operate.

The unintentional exposure was discovered June 13 when the original bacterial plates were gathered for disposal and B. anthracis colonies (live bacteria) were found on the plates. These plates had appeared negative for B. anthracis at the time samples were distributed to the other CDC laboratories. The review began immediately to assess the health risk, and those workers handling the plates were immediately notified.

CDC continues its internal review to determine why validated procedures were not used by the lab. Also, CDC has reported the incident to the Federal Select Agent Program. Learn more from coverage of this story in The New York Times.