USA TODAY -- Several dozen federal scientists in Atlanta may have been accidentally exposed to live anthrax after researchers in a bioterror lab violated procedures for inactivating the deadly bacteria, the Centers for Disease Control and Prevention announced Thursday.
The potential exposure of up to 75 researchers was discovered Friday when bacterial plates were being collected for disposal, but so far no researchers have shown any symptoms, the agency said in a statement. All are being offered two months of antibiotics and an anthrax vaccine injection.
"Out of an abundance of caution, CDC is taking aggressive steps to protect the health of all involved," the statement said. "Based on most of the potential exposure scenarios, the risk of infection is very low."
The agency said it does not believe that other CDC staff, family members or the public are at risk of exposure or need to take protective action.
"Incidents like this can't and shouldn't happen. It's unacceptable," said CDC spokesman Tom Skinner. "The safety of our employees is priority 1. We're getting to the bottom of how this happened and in the meantime we're taking immediate steps to reach out to those who were possibly exposed and make sure they are cared for properly."
Anthrax, which occurs naturally in soil, affects domestic and wild animals, and humans can become infected from close contact with them or animal products. The illness is not contagious.
Symptoms, which can mimic the flu or a cold, can first appear at any time between one day or more than two months, and the illness can be fatal if untreated.
The possible anthrax exposures come after USA TODAY and government auditors have previously flagged serious safety and security issues at the CDC's "high-containment" labs that work with potential bioterror agents.
In the latest incident, researchers at a high-security CDC lab transferred the samples to three other labs not equipped for live anthrax. The agency is investigating whether the samples, which are handled under strict procedures, contained live spores when they were passed along. Believing the samples had been inactivated, scientists at the other labs handled the specimens without wearing protective gear.
Between June 6 and Friday, procedures followed at two of the three labs may have aerosolized the spores, CDC investigators also found. The labs were closed and decontaminated, and will reopen when they are deemed safe.
The head of environment health and safety compliance, Paul Meechan, told Reuters all personnel at the bioterror lab had passed a security review and were found to be "stable, trustworthy individuals."
Because safety protocols were violated, disciplinary actions "will be taken as necessary," the agency said, and safety procedures will be reviewed with lab workers.
The CDC released few details Thursday about how the recent anthrax lapses occurred or what kind of staff were involved in the failed procedure to inactivate the bacteria, saying an internal review is ongoing.
Private government audits obtained last year by USA TODAY cited CDC for failing to ensure that those working with and around potential bioterror agents had received required training. A 2010 report said auditors couldn't verify that 10 of 30 employees sampled had required training. A 2009 report said the CDC labs "did not provide biosafety and security training to 88 of 168 approved individuals" before they were given access to work areas for bioterror agents.
In 2012, USA TODAY reported that a state-of-the-art $214 million lab building on the agency's main campus in Atlanta had experienced repeated problems with airflow systems designed to help prevent the release of infectious agents, government documents and internal e-mails showed. While agency officials said no one had been infected in the incidents that involved potentially contaminated air blowing outward into a "clean" corridor, a biosafety expert said the problems appeared to be major violations of laboratory operating standards.
Last year, USA TODAY used the Freedom of Information Act to obtain "restricted" reports from the U.S. Department of Health and Human Services' Inspector General. The usually private reports showed the CDC's labs have been repeatedly cited for failing to properly secure potential bioterror agents such as anthrax and plague, and not training employees who work with them.
House Energy and Commerce Committee Chairman Fred Upton, R-Mich., and the committee's oversight subcommittee chairman, Tim Murphy, R-Pa., said they were concerned about the latest incident. The committee has previously examined agency's lab lapses.
"There is no room for error or negligence when it comes to bioterror research and every precaution must be taken to ensure the safety of our scientists. The committee has been in contact with the CDC and will continue closely monitoring the situation," they said in a statement.