China banned trains and planes from leaving a major city at the centre of a virus outbreak on Thursday, seeking to seal off its 11 million people to contain the contagious disease that has claimed 17 lives, infected hundreds and spread to other countries.Authorities in Wuhan, a major transport hub, also suspended public buses and subways, and said residents should not leave "without a special reason".The coronavirus has caused alarm because of its similarity to SARS (Severe Acute Respiratory Syndrome), which killed nearly 650 people across mainland China and Hong Kong in 2002-2003.Like SARS, it can be passed among people through the respiratory tract.Wuhan residents shared their anguish on China's Twitter-like Weibo platform, with one describing being on the "verge of tears" when the de facto quarantine was announced.MUST READ | 5 things you need to know about the latest strain of coronavirus"We are feeling as though it is the end of the world," said another on Weibo, voicing concerns about shortages of food and disinfectant."We really need everyone's help."Wuhan's train station was almost empty except for workers and about a dozen people lining up for taxis, all of whom were wearing masks, according to an AFP reporter. The World Health Organisation on Wednesday delayed a decision on whether to declare a global health emergency - a rare instrument used only for the worst outbreaks.Urgency to stop spreadThe emergency committee will meet again on Thursday, after its chair, Didier Houssin, said the experts were split over declaring a public health emergency.WHO chief Tedros Adhanom Ghebreyesus said "more information" was needed but he also praised China's "very, very strong measures"."By having a strong action not only will they control the outbreak in their country but they will also minimise the chances of this outbreak spreading internationally," Tedros said when asked about Wuhan's transport shutdown.Full extent of crisis unknownAnimals are suspected to be the primary source of the outbreak, with Chinese health officials saying that the virus originated from the market where wild animals were illegally sold.ALSO READ | First US patient with China coronavirus is diagnosed in Washington StateStudies published this week suggest that the virus may have originated in bats or snakes.The WHO has confirmed that the virus can be passed between people, at least those in close contact, and Chinese health officials said Wednesday it could mutate and spread further.What's more, authorities have conceded they do not yet know the full extent of the crisis.