Police are guarding the Hong Kong hotel where the man stayed
About 300 people at a Hong Kong hotel have been placed under quarantine after a guest there became China's first confirmed swine flu case.
The 25-year-old man, who is now in hospital after testing positive for the virus, had travelled from Mexico via Shanghai, Hong Kong's leader said.
Local TV footage showed police wearing masks guarding the hotel exits.
Meanwhile, the UK joined Canada, Spain, Germany and the US in reporting person-to-person transmission of the virus.
On Friday, French Health Minister Roselyne Bachelot said two people were infected with swine flu, France's first confirmed cases.
South Korea has also confirmed its first case, local media said.
The announcements take to 16 the number of countries where swine flu has been confirmed.
Mexico, where the outbreak began, has shut down parts of its economy for five days in a bid to curb the virus's progress.
Late on Friday, Health Secretary Jose Angel Cordova announced the confirmed death toll from the virus had risen by one, to 16.
"The mortality rate isn't as great as could be expected," said Mr Cordova. "The majority of the deaths are women."
Mexican officials say the spread of swine flu - suspected in more than 380 deaths - is slowing.
International experts are more cautious - but one, Nancy Cox, chief of America's Center for Disease Control's influenza division, said the new virus lacked the traits that made the 1918 pandemic so deadly.
"We do not see the markers for virulence that were seen in the 1918 virus," she said.
In cases outside Mexico the effects of the virus do not appear to be severe, although one death of a Mexican child has been confirmed in the US.
The WHO has set its pandemic alert level at five - but says it has no immediate plans to move to the highest level of six.
In Hong Kong, the authorities have raised the alert level to emergency but urged residents to carry on life as normal.
Mexico: 176 suspected deaths - 16 confirmed
US: One death, at least 141 confirmed cases
New Zealand: 4 confirmed, 12 probable cases
Canada: 35 confirmed cases
UK: 11 confirmed cases
Spain: 13 confirmed cases
Germany: 4 confirmed cases
France: 2 confirmed cases
Israel, Costa Rica: 2 confirmed cases each
The Netherlands, Switzerland, Austria, Denmark, Hong Kong, South Korea: 1 confirmed case each
Countries with confirmed cases of secondary transmission
Some factories will stop production and schools are already closed. Residents have been urged to stay at home, but it is not clear how widely the shut-down order will be followed.
The number of confirmed cases of swine flu infection in Mexico now stands at more than 300, officials say.
Mexican Health Secretary Jose Angel Cordova said on Friday that three more deaths from swine flu had been confirmed, bringing the toll to 15.
Announcing the figure, Mr Cordova said that new cases of the virus were levelling off.
But Dr Keiji Fukuda, acting assistant director general of the World Health Organization (WHO), said fluctuations were to be expected.
In other developments:
• The US announces that it will buy 13 million new courses of antiviral treatment and send 400,000 of them to Mexico
• A flight from Germany to Washington DC is diverted to Boston after a female passenger complains of flu-like symptoms
• An aide to US Energy Secretary Stephen Chu who helped arrange President Barack Obama's recent trip to Mexico is being tested for swine flu, although the aide is said not to have been in contact with the president
• The head of the US Centers for Disease Control and Prevention says it is fine for people without flu symptoms to fly and use the subway, a day after Vice-President Joe Biden said he would advise his own family members against using public transport
• Denmark reports its first confirmed case of swine flu
• German authorities confirm that a nurse who treated a patient with swine flu also contracted the disease, in the first person-to-person transmission in the country
• Test results confirm the UK's first person-to-person transmission of swine flu, in a friend of a couple from Scotland who were first in the country to be diagnosed with the virus
Several countries have restricted travel to Mexico and many tour operators have cancelled holidays.
The WHO, meanwhile, says it will now call the virus influenza A (H1N1) rather than swine flu - which it says is misleading as pork meat is safe and the virus is being transmitted from human to human.
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