Officials said there is no indication the virus is spreading. "We do not have an epidemic," said Dr. Wilma Wooten, San Diego County health officer.

Family members and other people who know the two patients were being interviewed and tested, according to the paper.

Although it commonly causes respiratory problems in pigs, swine flu is rare in humans. Only 12 other cases of human infection have been detected since 2005, according to the U.S. Centers for Disease Control and Prevention (CDCP). Of the 12 cases, 11 of the patients had had contact with pigs.

Symptoms include fever, lethargy, cough and lack of appetite.

Documented cases of swine flu being transmitted from one human to another are rare, according to the CDCP.

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Editor:Yang Jie