CDC Lab Incident: Anthrax

Update: July 19, 2014

CDC Director Tom Frieden has issued a moratorium on the transfer of any infectious agents (active or inactivated specimens) from any of its biosafety level 3 (BSL-3) or BSL-4 laboratories to any other facility, inside or outside of CDC. This moratorium will remain in place pending review by a CDC laboratory advisory committee.

Dr. Frieden described the moratorium and other steps CDC is taking to create a strong culture of safety in the agency’s laboratories in a report pdf icon[PDF – 25 pages] released July 11, 2014, and during testimony pdf icon[PDF – 13 pages]external icon July 16, 2014, before the House Energy and Commerce Committee’s Subcommittee on Oversight and Investigations.

The following resources provide more details about recent lab incidents and corrective actions being taken at CDC:

Update: July 2, 2014

CDC is conducting 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. As a result, most of the affected employees have been determined to have no increased risk of exposure and are therefore being advised that they no longer need to take antibiotics and vaccine to prevent inhalation anthrax (CDC media statement).


CDC identified two potential risk groups and provided recommendations for each after reviewing recent laboratory studies, environmental sampling, a detailed risk assessment of each affected employee, and other information:

  • Staff who may have been potentially exposed to aerosols in affected laboratory space. These individuals are being advised to continue post-exposure prophylaxis (antibiotics and vaccine).
  • Staff who were not potentially exposed to aerosols but were in or near affected laboratory space. These individuals are being advised that they can discontinue antibiotics.

To date, 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 continues to take multiple steps toward preventing something like this from happening in the future. The incident is being investigated by a team from the US Department of Agriculture’s Animal and Plant Health Inspection Service. In addition, CDC’s Office of the Associate Director for Science is leading an internal investigation into the circumstances surrounding the incident. Based on these investigations, CDC will take appropriate action in the laboratory where best safety practices were not followed, as well as any actions indicated for all laboratories that work with dangerous microbes at CDC, and will consider broader implications for laboratory safety.


Update: June 27, 2014

CDC continues to investigate an incident in which staff in three of its laboratories may have been potentially exposed to live Bacillus anthracis (anthrax) bacteria after established lab safety practices were not followed. The health and safety of CDC staff is a top priority for the agency, and CDC is taking aggressive steps to monitor and protect the health of all involved, including dispensing or prescribing protective courses of antibiotics and vaccinations to potentially exposed staff. Based on what is currently known, CDC believes that other CDC staff, family members, and the general public are not at risk. None of the staff who were potentially exposed have developed anthrax to date.

What happened?

Early reports show that one of CDC’s biosafety level 3 (BSL-3) laboratories was preparing anthrax samples to be sent for research at two CDC labs with lower biosafety levels, both of them BSL-2 labs. The procedure used in the BSL-3 lab may not have fully inactivated the samples.

The two BSL-2 labs where the samples were sent are not equipped to handle live anthrax bacteria. Workers in the BSL-2 labs, believing the samples were inactivated, were not wearing adequate personal protective equipment needed to work with live bacteria while handling the material. Procedures used in two of the three involved labs also may have aerosolized the anthrax spores (put them into the air).

All three labs have been decontaminated. Two of these labs are not currently operating, and work there will not resume until they have been determined to be safe. The third lab has been determined to be safe and is now partially operational.

When did it happen?

The initial work in the BSL-3 lab occurred on June 5, 2014. The samples were transferred to the BSL-2 labs on June 6. However, it wasn’t until June 13 that laboratory staff discovered that the anthrax may not have been successfully inactivated. These samples had appeared to be negative for anthrax at the time the samples were distributed to the other CDC laboratories.

What is being done to protect CDC workers?

CDC immediately began investigating the incident to assess the health risk to staff. All work in the affected labs was suspended for decontamination. CDC notified potentially exposed personnel as soon as they were identified and referred them to the CDC health clinic or to a local emergency department for evaluation and preventive care. Potentially exposed staff are being offered antibiotics and vaccinations to prevent possible anthrax infection. No staff have shown symptoms of anthrax or tested positive for anthrax infection.

Anthrax cannot be spread from person to person. CDC believes that other CDC staff, family and friends are not at risk.

How is this incident being investigated?

CDC has reported the incident to the Federal Select Agent Program and the U.S. Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS). APHIS began conducting an independent investigation at CDC on June 24.

In addition, CDC is conducting an internal scientific review to determine why established procedures were not used by the lab.

CDC also performed environmental testing of the affected labs before they were decontaminated; preliminary results for some of the tests are negative for anthrax, suggesting that contamination or release was unlikely.

Where can I get more information about anthrax?

You can find more information about anthrax on CDC’s anthrax website. You can also see the original media statement in CDC’s Newsroom.