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As the coronavirus death toll climbs, the State Department announced plans Sunday to move personnel stationed in Wuhan, China, the epicenter of the outbreak, to the U.S. in a direct flight to San Francisco.

The department also said it will book a limited number of private U.S. citizens on a flight to San Francisco, scheduled to depart Tuesday. If demand is high, officials said, priority will be given to Americans at higher risk of coronavirus.

Chinese officials confirmed that 56 people have died from the virus.

Celebrations marking the start of the Lunar New Year were muted in China following the outbreak of the deadly coronavirus, which has now spread to four continents.

"It was like Chinese New Year but with a lot less people," Dr. Diana Adama, a U.S. citizen who lives in the city of Wuhan. "As of tonight they are going to cut off all the cars."

The unprecedented lockdown was expanded by Chinese authorities, who extended a transportation ban to 16 cities in the Hubei province — the epicenter of the outbreak, where at least 39 of the 56 people have died. The other two were in the provinces of Hebei and Heilongjiang.

As a result millions of people have been prevented from leaving the cities at a time when many travel to visit relatives in other parts of the country.

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In the city of Wuhan, which has a population of 11 million people, authorities banned most vehicles including private cars. Only authorized vehicles to carry supplies and for other needs will be permitted starting Sunday morning.

Public transportation was shut down earlier this week, as well as flights and trains out of the city.

As a result, many stayed home as numerous temples, major tourist sites and movie theaters were closed as authorities sought to limit the spread of the virus.

The city's U.S. consulate also announced on its Weibo social media channel that it had "temporarily suspended operations."

The Chinese National Health Commission said the number of people affected by the virus that causes respiratory infection in humans if untreated, to more than 1,200 people.

Wuhan is now closed off. No flights or trains out, and no mass transit within. Before dawn, we saw public buses parked on streets. A quarantine may seem a drastic move by #China's authorities but deemed crucial to contain the virus during the Lunar New Year travel rush. @NBCNews pic.twitter.com/hei8lS1Hjm — Janis Mackey Frayer (@janisfrayer) January 23, 2020

Meanwhile in Hong Kong, where five cases of coronavirus have been confirmed and 107 patients are under observation, Chief Executive Carrie Lam declared an emergency response.

The disease has now spread to four continents, as Australia announced its first case of the coronavirus Saturday. A Chinese man in his 50's who returned from China last week. Cases have also been reported in Malaysia, Vietnam, Japan, Taiwan, and other countries across Asia.

France said that three people had fallen ill with the virus — the disease's first appearance in Europe. And the United States reported its second case. A Chicago woman in her 60s who was hospitalized in isolation after returning from China.

The Chinese military dispatched 450 medical staff late Friday — some with experience in past outbreaks including SARS and Ebola — who arrived in Wuhan to help treat the patients hospitalized with viral pneumonia, the official Xinhua News Agency reported.

However, on Thursday, the chair of the World Health Organization emergency committee said it was "too early" to declare the coronavirus a global public health emergency.

The rapid increase in reported deaths and illnesses does not necessarily mean the crisis is getting worse, but rather it could instead reflect better monitoring and reporting of the disease, according to the Associated Press.

As many hospitals in the region reach capacity, Wuhan officials said they are rapidly constructing a new 1,000-bed hospital to deal with the crisis, to be completed Feb. 3. It will be modeled on a SARS hospital that was built in Beijing in just six days during the 2003 SARS outbreak.

The Chinese government, which is hoping to avoid a repeat of the deadly 2003 SARS outbreak, has warned officials not to cover up the spread of the virus. The South China Morning Post reported Tuesday that Beijing said anyone who withheld information would be “the sinner of a millennium to the party and the people” and would be “nailed on the pillar of shame for eternity.”