Across China, 15 cities with a combined population of over 57 million people — more than the entire population of South Korea — have been placed under full or partial lockdown.Wuhan itself has been effectively quarantined, with all routes in and out of the city closed or highly regulated. The government announced it is sending an additional 1,200 health workers — along with 135 People’s Liberation Army medical personnel — to help the city’s stretched hospital staff.Wuhan Mayor Zhou Xianwang said Sunday the number of cases could rise by another thousand.The disease has also spread widely across China, with almost 70 cases confirmed in the capital Beijing, including a nine-month-old girl — the youngest known case to be confirmed so far.China has extended the Lunar New Year holiday to February 2 in an attempt to dissuade people from traveling and spreading the virus further. Almost all mass celebrations for the festival have been canceled, and authorities have urged people to avoid holding traditional large family gatherings.The severity of the emerging crisis is evident in the government’s response. The Standing Committee of the Chinese Communist Party — the country’s top political body, headed by President Xi Jinping — has taken direct control of operations. Chinese Premier Li Keqiang arrived in Wuhan Monday to tour local hospitals, according to state media.More than 11 billion yuan ($1.58 billion) in government funds have been dedicated to the crisis.Worldwide effortThe virus has spread quickly around the world since it was first discovered in Wuhan last month. In a paper published Sunday, scientists at Imperial College London estimated that each person infected has gone on to spread the virus to two or three others. “This implies that control measures need to block well over 60% of transmission to be effective in controlling the outbreak,” they added.At a press conference on Monday, Professor Gabriel Leung of the University of Hong Kong warned that “self-sustaining epidemics” could be expected in major cities across China, now that the virus has spread there. Major cities such as Beijing, Shanghai, Guangzhou and Shenzhen, all of which have reported cases, could export infections to different places around the world. “We hope that with intervention in other cities in China, the situation will be more positive,” he said. “(However), containment measures may not always be effective, and will certainly be ineffective at some point in the long term.”Outside mainland China, at least 13 other places have reported cases of the virus, including France, Australia and the United States. Australia reported its fifth confirmed case Monday. Austria’s health ministry confirmed on Monday that one person had tested negative for the virus on Sunday, and that a female Chinese citizen was being tested — the outcome of that test is as yet unknown. In Hong Kong, authorities said residents of Hubei, the province of which Wuhan is the capital, and people who have visited the region in the last 14 days, will not be able to enter the city. The order does not cover Hong Kong residents, though they may be placed under quarantine. There were protests in the northern Hong Kong town of Fanling — near the Chinese border — after it was announced that an unoccupied apartment building there would be converted to a “temporary” quarantine center. Residents set up roadblocks and clashed with police, and on Sunday the authorities said they were abandoning the plan. Memories of the deadly 2003 SARS outbreak run deep in Hong Kong, and paranoia is already starting to settle in, with a rush purchases of face masks leading to shortages which may not be relieved until February, due to the Lunar New Year holiday and demand from China. Hong Kong leader Carrie Lam announced over the weekend that the threat level from the virus has been raised from “serious” to “emergency.” Schools in the semi-autonomous Chinese city will be suspended until February 17.On Thursday, David Heymann, the chairman of a World Health Organization (WHO) committee gathering data on the outbreak, said the virus spreads more easily from person to person than previously thought. “We are now seeing second and third generation spread,” Heymann said.In the US, where five cases of the disease have been confirmed, Nancy Messonnier, director of the US Center for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases, said that “we need to be preparing as if this is a pandemic, but I continue to hope that it is not.”Several countries, including the US, Australia, France and Spain are looking to repatriate citizens and government employees from China. Australia’s Health Minister Greg Hunt told national broadcaster ABC Radio Monday that Canberra was working on a plan to bring 100 “young Australians” out of Wuhan. “We are working to make sure that there’s support for those Australians and that we are there. We are also working on, as are other countries, to try to secure their ability to return to Australia,” Hunt said. France’s Health Minister Agnes Buzyn said on Sunday that France will fly its citizens back from Wuhan to France “in the middle of next week.” Buzyn said those who return to France will be monitored in one place for 14 days, to avoid any spread of the virus.A spokesman for the Spanish Foreign Ministry told CNN that it was “working with other European countries affected to organize a joint repatriation flight.”Tracing the virusSince the Wuhan virus was first identified in December, Chinese and international scientists have been studying it intensely, tracking its origin and working on a vaccine to fight it. Officials from the Chinese Center for Disease Control and Prevention (CDC) said Monday that they had successfully isolated the virus in environmental samples taken from a seafood and wildlife market in Wuhan believed to be the source of the outbreak. Thirty-three of the 585 environmental samples collected from the Wuhan’s Huanan Seafood Wholesale Market were found to contain the nucleic acid of the coronavirus, according to state-run news agency Xinhua. Of those samples, 31 came from the section of the market dedicated to the sale of wild animals, the CDC said. Chinese authorities announced Sunday that the trading of wild animals would be suspended nationwide, as experts lobbied for the government to put in permanent restrictions or even a ban. Any form of wildlife trade will be strictly prohibited on platforms including marketplaces, supermarkets, dining places and e-commerce sites, the Ministry of Agriculture and Rural Affairs and the National Forestry and Grassland Administration said in a statement. All sites were wild animals are raised will be quarantined. Considerable attention has been paid on both the Chinese internet and in the western tabloid press to the eating of wild animals in parts of China — particularly bats and civet cats, a mammal native to Asia that was previously linked to the 2003 SARS outbreak. CNN’s David Culver and Yong Xiong in Wuhan; Steven Jiang in Beijing; Helen Regan, Carly Walsh, Yuli Yang, Chermaine Lee, Alexandra Lin, Isaac Yee, Angus Watson, and Sophie Jeong in Hong Kong; Yoonjung Seo in Seoul; and Junko Ogura in Tokyo contributed reporting.