CDC lab workers unintentionally contaminated non - dangerous bacterial strain with H5N1 . Reports : This happened because scientists failed to follow ` ` best practices '' CDC scientists found out about cross - contamination several weeks after it happened .
CDC lab workers unintentionally mixed non-dangerous flu strain with H5N1 . Reports : Contamination happened because scientists failed to follow `` best practices '' CDC director found out about cross-contamination several weeks after it happened .