ATLANTA – The Centers for Disease Control and Prevention (CDC) closed a laboratory that mishandled samples of bird-flu virus, but the closure should not impact the CDC's work on influenza vaccines, according to Tom Frieden, director of the CDC.

"We're confident that we'll be able to get the flu lab reopened in time to do the essential work it does like helping to prepare the influenza vaccination for Americans in tracking the spread of flu around the world and around the country," Frieden said at a recent news conference. "So, at this point, we don't see any risk to keeping the lab closed until we have a full assessment of what happened and are sure that we can prevent future occurrence."

CDC officials learned that researchers at the agency's influenza lab accidentally cross-contaminated a less-harmful strain of animal influenza with highly pathogenic H5N1 influenza. The incident occurred as researchers were preparing to ship the less-harmful strain to a partner laboratory. Six weeks passed before Frieden was told about the incident.

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Two other laboratory mistakes led to CDC researchers being exposed to anthrax, and vials of smallpox were found on the National Institutes of Health campus in Maryland. Frieden said the samples were dated Feb. 10, 1954, before smallpox eradication was undertaken.

In response to the safety lapses, Frieden implemented a series of reforms such as a moratorium on biological material leaving biosecurity level 3 and 4 laboratories, and appointing Dr. Michael Bell director of laboratory safety.

"These events should never have happened," Frieden said. "Together, these events I’m sure have many people asking and questioning government labs. They may be wondering whether we're doing what we need to do to keep our workers and our communities safe — and I think it's fair to raise those questions.

"I’m disappointed by what happened, and frankly, I’m angry about it," he concluded.