A fourth person in Canada has the coronavirus, first testing negative, then positive before recovering quickly as health officials scramble to get a handle on the fast-moving infection. The female university student in her 20s arrived in Toronto on January 23 from Wuhan, China, the epicentre of the outbreak. Initially asymptomatic, she reported to hospital the next day, where she initially tested negative. A second test at Canada’s National Microbiology Laboratory in Winnipeg, Manitoba, confirmed the case as positive. “It is clear that we are learning more and more about the coronavirus each day, and our testing procedures are evolving and getting more and more precise,” Ontario’s Chief Medical Officer of Health Dr David Williams said in a statement after a news conference in Toronto. Health officials globally are struggling to understand the nature of the disease and how it is transmitted, as well as how to diagnose it. There are reports that it can be passed by people before they show symptoms but not all health officials believe this is the case. There is still no “hard evidence” that a person without symptoms is infectious, Barbara Yaffe, Toronto’s associate chief medical officer of health said at the news conference. The female patient’s viral load was extremely low and she fully recovered in two to three days but remains in isolation, officials said. “The risk continues to be very low for Ontarians,” Williams added at the news conference. The new Ontario case brings the number of infected in Canada to four, with one in British Columbia. The first confirmed instance of the virus was announced January 25. In the first case, a man in his 50s, who had travelled from Wuhan via Guangzhou, checked into a Toronto hospital a day after he landed on January 22. He is still recovering, indicating recovery times are not the same across the board, health officials said. US bans foreign travellers from China in coronavirus ‘public health emergency’ Canada’s top diplomat, meanwhile, received a nod from his Chinese counterpart to bring home nearly 200 Canadians from Wuhan, the epicentre of the coronavirus epidemic, his office said on Friday. In a rare telephone call with Foreign Minister Wang Yi on Thursday night, Canada’s Foreign Minister François-Philippe Champagne “asked for the collaboration of the Chinese government in helping those Canadian citizens who want to depart the region”. Wang “responded positively,” he said in a statement. Ottawa chartered a plane to bring back 196 Canadians who asked to be repatriated, but the airlift had remained in limbo this week even as the United States, Japan, South Korea and European nations brought home their nationals. With Wuhan locked down as part of a government effort to contain the epidemic, the Canadian flight required authorisation to land in the region. Canada’s relations with its second biggest trading partner have been strained since the arrest on a US warrant of Huawei executive Meng Wanzhou in December 2018 during a flight stopover in Vancouver. China has detained two Canadians, former diplomat Michael Kovrig and businessman Michael Spavor, in apparent retaliation. It has also blocked Canadian agricultural shipments. The first phase of a court hearing of a US request for Meng’s extradition was held earlier this month, and is expected to resume in April. US public health agency orders mandatory quarantine for Wuhan evacuees Kovrig and Spavor, meanwhile, remain in China’s opaque penal system. Champagne’s office said he also raised the plight of the detained Canadians with Wang, adding: “The two agreed to remain in touch on issues of mutual importance.” Also on Friday, Prime Minister Justin Trudeau and US President Donald Trump agreed in a telephone call “on the need for [Kovrig and Spavor’s] immediate release”. Additional reporting by Agence France-Presse Purchase the China AI Report 2020 brought to you by SCMP Research and enjoy a 20% discount (original price US$400). This 60-page all new intelligence report gives you first-hand insights and analysis into the latest industry developments and intelligence about China AI. Get exclusive access to our webinars for continuous learning, and interact with China AI executives in live Q&A. Offer valid until 31 March 2020.