HONG KONG (Reuters) - Chinese authorities have identified the southern province of Guangdong, home to Asia's biggest African population, as a frontline in their efforts to prevent the deadly Ebola virus from entering mainland China. The province bordering Hong Kong has proven susceptible to infectious diseases in the past, shouldering a large share of SARS and bird flu cases, prompting local authorities to take no chances with Ebola. Local authorities say they have expanded testing procedures at provincial entry ports and 27 hospitals have been designated to handle possible Ebola cases. Travelers arriving from Ebola-affected nations must leave their contact details. "The central government has asked Guangzhou to strengthen preventative measures," Mao Qun'an, a spokesman for the Ministry of Health, told Reuters. "Of course in Guangzhou, there are many people from outside China's borders." As many as 190 flights connect Guangdong and Africa each month, ferrying thousands of traders, many of whom come from the Ebola-hit nations of Sierra Leone, Liberia and Guinea. More than 60 percent of the passengers arriving on the mainland from West Africa arrive in Guangdong. China has not reported any confirmed cases of the deadly virus, though several suspected cases have ended up in hospital for observation. At this week's Canton Fair in the provincial capital Guangzhou, China's biggest trade exhibition, medical workers donned full protection suits and checked visitors for signs of the Ebola virus that has killed nearly 5,000 people, mostly in West Africa. "Of course we are worried," said a police guard at the fair who identified himself only by the name Sun. "People are coming from all over the world." The Guangdong Provincial Center for Disease Control and Prevention has conducted tests on about 50 people from West Africa, all returning negative results, the China Daily reported on Thursday. The center and health officials in Guangdong could not be reached by Reuters for comment. AFRICAN TRADERS Authorities' main concern revolves around the large number of African traders, many of whom come from West Africa, in Guangzhou. The city is a booming marketplace for cheap goods that are exported to Africa. Officially, about 15,000 Africans live in Guangzhou, but there are many illegal immigrants and some reports put the number at 10 times that figure. The official Guangzhou Daily said 438,000 Africans passed through the city from January to October this year. Frank, 37, a trader from Nigeria who has lived in China for 10 years, said Ebola was a sensitive subject given many Africans were staying in Guangdong illegally, raising concerns that victims would avoid visiting public hospitals. Nigeria itself was declared Ebola-free by the World Health Organization last week, having contained the spread of the disease after 20 people were infected. Seven of those died. "It's a very big problem," Frank said. "Without a valid visa, you can do nothing in this country ... We don't talk about it." Authorities in Guangzhou have launched a campaign warning of the dangers of Ebola, but African immigrants complain they have received little information. "There's nothing much we can do," said a 30-year-old Kenyan man by the name of Pawsi. "I don't know what the government has done. I can't read Chinese." State media reported on Wednesday that people returning to Beijing from regions affected by Ebola should quarantine themselves at home for 21 days and undergo twice daily temperature checks if they have had contact with patients. China's health ministry has identified the main airports in Beijing, Shanghai and Guangzhou as key in terms of risk, and has been focusing its initial health and temperature checks there. "Beijing has experience with SARS and the H7N9 (bird flu) virus. Once there is a case of Ebola, we have the ability to control its spread," city health official Zhao Tao told the official Xinhua news agency. There is much scepticism about the government's transparency. In 2003, Chinese officials covered up the spread of Severe Acute Respiratory Syndrome (SARS) for weeks before a growing death toll and rumors forced the government to reveal the epidemic, apologize and vow full candor in future disease outbreaks. But in 2013, the government earned praise from the international community for being transparent on an outbreak of a deadly new bird flu in humans.