Officials Race to Destroy Samples A dangerous strain of the flu virus that caused a worldwide pandemic in 1957 was sent to thousands of laboratories in the United States and around the world, triggering a frantic effort to destroy the samples to prevent an outbreak, health officials revealed yesterday. Because the virus is easily transmitted from person to person and many people have no immunity to it, the discovery has raised alarm that it could cause another deadly pandemic if a laboratory worker became infected, officials said. As a result, health authorities were urgently working to make sure all samples...