A worker at a Centers for Disease Control and Prevention laboratory harvests avian flu viruses for sharing with other laboratories in 2013.

A worker at a Centers for Disease Control and Prevention laboratory harvests avian flu viruses for sharing with other laboratories in 2013.

CDC/James Gathany

CDC explains mix-up with deadly H5N1 avian flu

A federal scientist may have accidentally contaminated a relatively benign avian influenza strain with the deadly H5N1 bird flu virus in part because he or she was overworked and rushing to make a lab meeting, according to an internal report released today by the Centers for Disease Control and Prevention (CDC).

In the March incident, CDC sent a sample of low-pathogenicity H9N2 bird flu virus that a lab had unknowingly contaminated with H5N1 to a U.S. Department of Agriculture (USDA) lab, which discovered the mistake when test chickens died. CDC Director Thomas Frieden first disclosed the incident in July at a press conference about other lab accidents. Frieden was especially troubled, he said, because the H5N1 incident was not reported to top CDC leaders for 6 weeks.

According to the 16-page report released today, the H9N2 sample probably became contaminated with H5N1 on 17 January when an experienced researcher did not follow proper decontamination or other protocols between inoculating cell cultures with the H9N2 flu strain and H5N1 using the same biosafety cabinet. The worker was “being rushed to attend a laboratory meeting at noon” and was also under a “heavy workload” as his or her team hurried to generate data for a February vaccine meeting at the World Health Organization, the report says.

The CDC flu lab sent USDA an H9N2 sample on 12 March; the USDA lab notified CDC of the contamination on 23 May. The delay in reporting resulted in part from unclear CDC rules for reporting incidents with select agents. Contaminated samples were also sent to another CDC lab, the report says. Workers were unlikely to have been exposed, however, because the samples were handled under enhanced biosafety-level 3 conditions, which includes many safety measures such as workers wearing protective suits and respirators.

The report describes new training and operating procedures to prevent future incidents, along with CDC-wide safety reforms already under way including closing the flu lab.

In a lengthy USA Today article about the report, CDC official Anne Schuchat called the mistakes “unacceptable” and said: "We just don't think shortcuts are permissible when working with these kinds of dangerous pathogens." Among measures that CDC is taking are disciplinary actions, Schuchat said.

*Correction, 19 August, 12:05 p.m.: The photo credit was incorrect; it has been fixed.

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