Hong Kong is to impose a mandatory 14-day quarantine on all visitors from mainland China as it battles to prevent the spread of a coronavirus outbreak.
The policy comes into effect on Saturday but officials refused to close the border entirely, as demanded by medical staff who have gone on strike.
Hong Kong, which has 21 confirmed cases and one fatality, suffered 300 deaths in the Sars outbreak in 2002-03.
There are 24,300 confirmed coronavirus cases and 490 deaths on the mainland.
Those figures included an additional 4,000 cases and 65 deaths on Tuesday.
The virus has spread overseas, with 25 nations confirming a total of 191 cases, although there has so far been only one death, in the Philippines.
The World Health Organization (WHO) has declared the outbreak a global health emergency. Its chief, Tedros Adhanom Ghebreyesus, on Wednesday appealed for $675m (£520m) to fund a three-month response plan .
Meanwhile, at least 10 people on board a cruise ship docked in the Japanese port of Yokohama have tested positive for the virus.
The coronavirus causes severe acute respiratory infection and symptoms usually start with a fever, followed by a dry cough. Most people infected are likely to fully recover – just as they would from a flu.
Chief Executive Carrie Lam said anyone arriving from the mainland, including foreigners, would be quarantined for 14 days from Saturday, although she did not say how this would be imposed.
It is unclear where the quarantines would take place or whether Hong Kong residents could spend the time at home.
Tens of thousands of people arrived from the mainland on Tuesday.
Ms Lam has not moved to close the border entirely, although thousands of medical staff on Wednesday entered the third day of their strike over the issue and have threatened to escalate their action.
Hong Kong will, however, close the Ocean and Kai Tak cruise terminals.
Some 3,600 passengers and crew on the World Dream, docked at Kai Tak, are being tested for the virus after three Chinese passengers who were on the ship between 19 and 24 January tested positive after disembarking.
Hong Kong remains concerned about a repeat of the deadly Severe Acute Respiratory Syndrome (Sars) outbreak, although the mortality rate of the new virus is much lower than that of Sars, which was around 9.6%.
There have been massive queues for masks which are in short supply and are selling at inflated prices.
Separately, the Hong Kong-based airline Cathay Pacific is asking 27,000 staff to take three weeks unpaid leave over the coming months as it deals with the impact of the outbreak.
Officials say they have stepped up efforts to control the outbreak, particularly in its epicentre, Hubei province and its capital, Wuhan, where two hospitals have been speedily built and 11 public venues sports transformed into makeshift wards.
Millions in Hubei and Zhejiang provinces have been told only one person per household can go outside every two days.
Chinese health authorities insist suspected cases are falling, because of better testing.
Foreign ministry spokeswoman Hua Chunying urged other nations to be objective in their assessment of the virus and support China’s efforts. “Fear is worse than any virus,” she said.
State broadcaster CCTV quoted doctors in Wuhan as saying it appeared that pregnant women could pass the virus to their unborn child. A baby had tested positive after being born to an infected mother in the city.
Announcing the appeal for $675m, Dr Tedros said: “Our message to the international community is invest today or pay more later.”
The vast majority of the funds would go to nations needing help to protect against the virus. Some 500,000 masks and 40,000 respirators would be sent to 24 countries.
Dr Tedros said a “window of opportunity” existed to bring the virus under control and also welcomed a $100m donation from the Bill and Melinda Gates Foundation announced on Wednesday.
The WHO also played down reports from Chinese TV that researchers at Zhejiang University had found an effective drug, saying there were still “no known effective therapeutics”
In other developments on Wednesday:
Almost 300 of the 3,700 people on the ship, the Diamond Princess, have been tested so far. The number of infected could rise from the 10 so far confirmed.
Those infected have been taken to hospitals but the rest of the crew and passengers on board are in quarantine.
The checks began after an 80-year-old Hong Kong man who had been on the ship last month fell ill with the virus.
British tourist David Abel, who is on board, told the BBC he was supposed to return to the UK on Tuesday.
“We had a flight booked with BA on Tuesday morning and that has had to be cancelled. We’ve got no idea when we are going to be allowed off the ship,” he said.
“We’ve got no interaction with other passengers, food is brought to the room. It’s really basic food, nothing like we’ve enjoyed on the cruise at all.”