The Centers for Disease Control and Prevention says that at least 52 workers are taking antibiotics as a precaution because of a lab safety problem that may have accidentally exposed them to anthrax.

Bacillus anthracis vegetative cells in a monkey spleen. Anthrax is an infectious disease caused by the spore-forming bacteria Bacillus anthracis. (AP Photo/Anthrax Vaccine Immunization Program, File)

So far, the CDC's occupational health clinic has seen 54 out of 86 potentially exposed employees. Only two have refused antibiotic treatment, which can cut the chances of infection after exposure to the germ. The CDC says 27 of them also began receiving an anthrax vaccine.

The safety lapse occurred when a high level biosecurity lab failed to completely inactivate anthrax samples sent to less secure labs for further research. The problem was discovered last Friday and CDC revealed it on Thursday.

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