"Strong progress" has been made in calming Democratic Republic of Congo's deadly Ebola outbreak in a city of 1.2 million and in the rural outpost where the epidemic was declared one month ago, the World Health Organisation said on Friday, but now the focus turns to "some of the most remote territory on Earth."Health officials expressed cautious optimism as the pace of new cases has slowed. DRC's health ministry late on Thursday announced a new confirmed Ebola case, bringing the total to 38, including 13 deaths.The new case is in the remote Iboko health zone in DRC's northwest. Health workers also have been chasing contacts of those infected in Mbandaka city, a provincial capital on the heavily traveled Congo River, and in Bikoro town where the outbreak was declared.While Ebola's spread to a major city has complicated efforts to track all contacts of those infected, the presence of the virus in Iboko poses another world of problems.The forested terrain is so rough that even four-wheel-drive vehicles can't reach the area, which has no electricity, WHO's emergency response chief Peter Salama told reporters in Geneva. Motorcycles are only now arriving and health workers are sleeping 15 to 20 people to a tent."This is a major logistical and boots-on-the-ground epidemiological endeavor now," Salama said, adding that work there will go on for weeks.WHO has vaccinated more than 1 000 people over the past two weeks in all areas of the outbreak, including health workers who are at high risk. The virus spreads via bodily fluids of infected people, including the dead."There's been very strong progress in the outbreak response, particularly in relation to two of three sites," Salama said. "Phase one, to protect urban centres and towns, has gone well and we can be cautiously optimistic."He warned, however, that experts are not in a position to document all chains of transmission of the virus, so "there may still yet be unknown chains out there and there may still be surprises in this outbreak."This is DRC's ninth Ebola outbreak since 1976, when the hemorrhagic fever was first identified.WHO said it is supporting emergency response and preparedness efforts by nine neighbouring countries. Republic of Congo and Central African Republic are closest to the outbreak and are highest priority, but DRCi s also bordered by Angola, Burundi, Rwanda, South Sudan, Tanzania, Uganda and Zambia.WHO says the Ebola response will cost more than $15.5m over nine months.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.