Meet the child known as "patient zero" by his doctors -- 5-year-old Edgar Hernandez, who survived the earliest documented case of swine flu in an outbreak that, officials say, has now spread across four continents.

His mother blamed the virus on a huge pig farm in the neighborhood. Officials have conducted tests at the farm owned by U.S. company Smithfield Foods, and those tests came back negative.

Earliest case of swine flu tucked away in Mexico, officials say - CNN.com