Visitors must isolate themselves in hotel rooms or government-run centres. Residents must stay inside their homes.
Anyone caught flouting the new rules faces a fine and a prison sentence.
The 60-year-old US citizen, the first confirmed non-Chinese victim of the illness, died on Thursday at Jinyintan Hospital in Wuhan, the epicentre of the outbreak, according to a US embassy spokesman in Beijing, who did not give details.
Separately, the Japanese foreign ministry said a man in his 60s died, also in Wuhan, from what was suspected to be a case of coronavirus. However, it said it could not confirm the diagnosis, and that Chinese officials said the cause of death was viral pneumonia.
China reports 34,546 coronavirus cases
The city is opening its second makeshift hospital since the outbreak began. Leishenshan hospital was built in two weeks and will be able to accommodate 1,500 patients.
The number of confirmed cases in mainland China stands at 34,546. Outside China, 270 cases have been confirmed in 25 countries, according to the World Health Organization (WHO), with two fatalities – one in Hong Kong and another in the Philippines.
On Saturday, France confirmed five new cases in its Haute-Savoie region, including a nine-year-old boy and bringing the total of infected in the country to 11.
French Health Minister Agnès Buzyn said all of the five new cases were British nationals staying in the same chalet, which had also housed a Briton who had been in Singapore. Their condition is not said to be serious. A further six people who stayed at the chalet are under observation.
Two schools – one the nine-year-old boy has been attending, along with another school where he has French classes – have been closed as a precaution.
26 confirmed cases in Hong Kong
In Hong Kong, there have been 26 confirmed cases. Tens of thousands of travelers queued at the Chinese border city of Shenzhen to beat the Friday midnight deadline.
But by Saturday morning, only a trickle of people were arriving via the Shenzhen Bay Port crossing.
In a press conference, Hong Kong chief executive Carrie Lam said the territory’s government only has 12 million face masks, which she expects to be used up within one month. She appealed for anyone with resources to buy masks to “donate them to people in need”.
Meanwhile, three more people have tested positive for the virus on a quarantined cruise ship in Yokohama harbour, bringing the total number of cases on board to 64.
There was some positive news on Friday when the WHO said there had been fewer reported infections in China in the past two days. However, its director general, Tedros Adhanom Ghebreyesus, cautioned against reading too much into those figures.
He also told reporters that the outbreak had caused a global shortage of protective medical equipment such as gowns, masks and gloves.
“When supply is short, and demand is high then there could be bad practices like hoarding in order to sell them at higher prices,” he warned, urging suppliers to “uphold the protection of humanity” rather than looking to increase profits.
The WHO also released new data from 17,000 patients that suggested 82% had a mild form of the disease, with 15% considered severe cases and 3% critical.