Hong Kong's efforts to keep the deadly Ebola virus at bay could be stymied by the reluctance of African visitors to give contact details to health officials, the city's health protection chief said. Dr Leung Ting-hung, controller of the Centre for Health Protection, said it would be difficult to follow the lead of Macau and make daily contact with visitors from areas affected by the deadliest ever outbreak of the virus, which has killed more than 700 people since March. "Each place has its own way of preventing the virus," Leung said. "For Hong Kong, the difficulties are that some tourists do not buy sim cards to use mobile phones here, or some of them are reluctant to leave their local contacts." The city announced new measures on Saturday to keep the disease at bay. They include handing leaflets to passport-holders from the worst affected countries - Guinea, Liberia and Sierra Leone - reminding them to report to health officers if they feel ill on arrival. Leung estimated that 4,000 visitors from West Africa arrived in the city each year. Macau announced on Thursday that citizens of the three countries would undergo health checks on arrival. Those suspected of carrying Ebola would be put in isolation to undergo checks. Those not showing symptoms would be contacted by phone every day of their stay. But Leung said public education to promote health awareness among both tourists and locals would be more effective. The city had an Ebola scare on Wednesday, after a woman returned from Kenya exhibiting fever, dizziness and vomiting - the initial symptoms of the virus. But she tested negative, and Leung said the city had not had any suspected cases so far. Any patient displaying Ebola symptoms would be kept in isolation at Princess Margaret Hospital in Kwai Chung, he added. Video: What is the Ebola virus Leung also dismissed concerns Chungking Mansions - the maze of guesthouses, cheap restaurants and stores in Tsim Sha Tsui that is a favoured haunt of Africans - could become ground zero for an Ebola outbreak. "Many of those who stay in Chungking Mansions have been living in Hong Kong for quite some time," he said. The centre has set Ebola guidelines for health professionals and said on Saturday that it would write to doctors and hospitals to stress the importance of infection control measures.