A Hong Kong woman who recently developed symptoms of respiratory infection and fever while traveling to the United States was being tested for swine flu, the local Center for Health Protection (CHP) said Monday.

Hong Kong stepped up surveillance of swine flu on Saturday. The Center for Health Protection said it has since received reports on three patients in line with the reporting criteria. All-clear has been given to the other two patients.

The 27-year-old woman developed the symptoms last Thursday in San Francisco and went back to Hong Kong on Friday. She was admitted to a local hospital on Sunday and was now in stable condition, said the Center for Health Protection, a unit of the Department of Health of the Hong Kong Special Administrative Region (HKSAR) government.

"Laboratory analysis on a respiratory tract specimen taken from her yielded positive results for human influenza A H3 subtype, which is not swine influenza," the CHP said in a statement.

"We still don't know the results of the tests for swine flu," the Information Services Department of the HKSAR government said in reply to a phone inquiry.

Thomas Tsang, controller of the CHP, said earlier that there has been no reported case of swine flu in San Francisco so far.

Hong Kong stepped up surveillance of swine flu on Saturday. The Center for Health Protection said it has since received reports on three patients in line with the reporting criteria.

The other two patients, a 77-year-old woman and her four-year- old granddaughter, both tested negative for influenza A at a local hospital early this morning.

The woman had traveled to the United States and Mexico from April 3 to 19. She and her granddaughter sought treatment at the local hospital on Sunday night.

Both the woman and her granddaughter were in stable condition now.

The CHP said leaflets with health messages have been distributed at the airport to passengers arriving from places where human cases of swine flu were reported.

Surveillance and preventive measures being put in place at all control points would be under constant review and amended if necessary to keep abreast of the latest developments in the outbreaks of swine influenza A (H1N1) overseas, it added.

(Xinhua News Agency Apirl 28, 2009)