The mayor of New Orleans, Louisiana, has been quarantined in China after possible exposure to the H1N1 virus, his office said Sunday. Mayor Ray Nagin, who traveled to China on an economic development trip, flew on a plane that carried a passenger being treated for symptoms suspected to be from the virus, commonly known as the swine flu virus, the mayor’s office said in a statement. Nagin, his wife and a member of his security detail have been quarantined in Shanghai, China, though all three are symptom free, the statement said.