HONG KONG, China (CNN) -- In Hong Kong, where the alert level has been raised to "emergency" after reporting its first case of swine flu, authorities are trying to keep the H1N1 virus from spreading through the metropolis of 7 million people through quarantine, stepped-up border measures and surveillance.
Quarantined guests and hotel employees wave through the glass of the main entrance of Hong Kong's Metro Park Hotel.
The quarantine has extended beyond the single confirmed case, a 25-year-old Mexican man, to include more than 340 people.
They include: two taxi drivers, two fellow taxi passengers, a local friend, 36 passengers within a three-row vicinity of the patient aboard a China Eastern flight from Shanghai to Hong Kong, and 300 guests and staff at the Metropark Hotel he checked into.
All have been put on the antiviral drug, Tamiflu.
Among the two cab drivers, one was suspected of taking the patient from the airport to the hotel, and another was believed to have taken him from the hotel to the hospital.
Authorities are seeing another 40 to 50 guests whose names are on the hotel's guest list. Some of them left their luggage behind.
"They are gambling with their health, jeopardizing public health safety," said Dr. York Chow, secretary for Food and Health, appealing to the guests to come forward.
In addition to the Metropark Hotel in Wanchai district, the Lady Maclehose Holiday Village is being used as an isolation center during the one-week quarantines.
The government has assured that people under quarantine will have their visas automatically extended, their hotel lodging fees waived and their onward journeys prepared. The Wanchai hotel is providing guests $200 worth of free overseas telephone calls daily.
The isolation order, which went into effect Friday night, is to expire Friday at 8:30 p.m. (8:30 a.m. ET) -- the length of an incubation period for swine flu.
The isolation order did not extend to the air crew or remaining passengers aboard the China Eastern flight.
An airplane's air exchange rate is high compared to that in an office or hotel, explained Yuen Kwok-yung, chair of infectious diseases at the University of Hong Kong. "Risk is very low on a plane," he said.
So far, there have been no further confirmed cases of swine flu, and no Hong Kong pigs have tested positive for the virus, Yuen said.