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The Centers for Disease Control and Prevention has been trying to understand how a lab error there may have exposed dozens of workers to anthrax. And in the course of that investigation, officials learned about another serious mistake that went unreported to top brass for more than a month. It involves a potent strain of flu. There's no apparent public risk but NPR's Richard Harris reports that officials now recognize a pattern of problems in the world-class laboratory.
RICHARD HARRIS, BYLINE: Earlier this year scientist at the U.S. Department of Agriculture ask the CDC for a sample of a regular old variety of flu virus for some experiments. CDC director Tom Frieden said his researchers packaged it up carefully and sent it along to this other secure laboratory.
TOM FRIEDEN: In the process, unknowingly, they cross contaminated that strain with highly pathogenic H5N1 influenza.
HARRIS: A flu virus that's very nasty indeed. The USDA scientist noticed that they weren't dealing with a simple flu virus they had asked for and the CDC confirmed that it had sent a contaminated sample.
FRIEDEN: Everything we know today suggests that there was no human exposure, the materials are all either destroyed or contained and there's no risk from it. What's distressing about it are two things really. First our influenza laboratory is a superb laboratory, so to me the fact that something like this could happen in such a superb laboratory is unsettling.
HARRIS: It suggests deeper safety problems at CDC. Frieden was also disturbed that he didn't learn about the incident until this week, which is six weeks after it came to light.
FRIEDEN: It's very important to have a culture of safety that says, if you've got a problem, talk about it.
HARRIS: As Frieden dug into this and a similar incident recently in which anthrax was mishandled, he reviewed six incidents over the years where CDC safety procedures had failed he says, each time people fix the smaller problem at hand without realizing the context he now sees.
FRIEDEN: There's a problem and it's a symptom of a broader problem of laboratory safety.
HARRIS: Frieden today announced a series of actions to address this, including a moratorium on moving material out of the CDC's highest security labs and a safety review including outside experts. One bit of more positive news is that an anthrax lab accident last month apparently did not end up exposing anyone to this deadly germ.
FRIEDEN: We're very concerned about the health and well-being of our own staff and the fact that they had to deal with uncertainty, stress, potential risk, had to take preventive medicines that can have adverse event - as a result of this incident is something that I feel terrible about and I wish had not happened.
RON ATLAS: It's fortunate that these have not posed a real safety risk to either laboratory workers or to the general public. But it could have.
HARRIS: Ron Atlas is with the American Society for Microbiology and a professor at the University of Louisville. He says it's a stark reminder to lab workers everywhere that you can get lulled into a sense of complacency, even when working with dangerous materials. Marc Lipsitch at Harvard University takes that one step farther.
MARC LIPSITCH: I don't think this is a CDC problem, I think CDC is being open about what has happened in several instances there. But their own prior research has shown that around the country in high containment laboratories there are errors on almost a weekly basis.
HARRIS: Those apparently haven't ended up causing big problems he says, in part because most of the germs in question don't spread very easily.
LIPSITCH: The problem is that now people are starting to do experiments with much more contagious pathogens, particularly making novel contagious strains of flu and the human error factor can't be reduced.
HARRIS: So scientist like Lipsitch are calling for this research to be reined in. Richard Harris, NPR News.
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